Hi,
I am experiencing issues in flashing nRF52840 on a custom board I have. I have 10 boards, and only 2 work. The rest of 8 seems to have the exact same issue. At this point, I've gone through checked and re-checked all of the schematics, gerbers, assembly of the boards - they all seem identical. Yet I have 2 boards that work fine.
I am using Segger J-Link Plus debugger and here is the SDK and nrfjprog versions:

Here is the breakdown of what I am seeing. When I try to flash using VSCode + nRF Connect SDK extension, I see this message:

As a side note, it seems impossible to add the "--log" to the west command line as I get another failure.
Instead of flashing, I just want to read some memory from the device. By searching the Nordic forums I found a post about checking if the device is constant reset and clear it (link). So I ran that command line on a bad board and I get same failure.
On a good board, everything works fine.
Here is the log output of the "memrd" command line from a board that does not work.
[2023-Jan-26 17:36:56] [ info] --------------------------------------------------------------------------------
[2023-Jan-26 17:36:56] [ info] C:\Program Files\Nordic Semiconductor\nrf-command-line-tools\bin\nrfjprog.exe --memrd 0x10001200 --w 32 --n 8 --log . --family NRF52
[2023-Jan-26 17:36:56] [ info] nrfjprog version 10.12.1
[2023-Jan-26 17:36:56] [ info] --------------------------------------------------------------------------------
[2023-Jan-26 17:36:56] [debug] [ nRF0x0] - open_dll
[2023-Jan-26 17:36:56] [ info] [ nRF0x0] - Load library at C:\Program Files\Nordic Semiconductor\nrf-command-line-tools\bin\JLINKARM_NRF52_NRFJPROG.dll.
[2023-Jan-26 17:36:56] [ info] [ nRF0x0] - Library loaded, loading member functions.
[2023-Jan-26 17:36:56] [ info] [ nRF0x0] - Member functions succesfully loaded.
[2023-Jan-26 17:36:56] [ info] [Backend] - Logger callback at 0x7ff7a1ac56f0 registered in Segger backend logger.
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Logger callback at 0x7ff7a1ac56f0 registered in JLink logger.
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - open
[2023-Jan-26 17:36:56] [debug] [Backend] - open_dll
[2023-Jan-26 17:36:56] [ info] [Backend] - No J-Link DLL path was provided. Attempting to auto detect.
[2023-Jan-26 17:36:56] [ info] [Backend] - Load library at C:\Program Files\SEGGER\JLink\JLink_x64.dll.
[2023-Jan-26 17:36:56] [ info] [Backend] - Library loaded, loading member functions.
[2023-Jan-26 17:36:56] [ info] [Backend] - Member functions succesfully loaded.
[2023-Jan-26 17:36:56] [debug] [Backend] - dll_version
[2023-Jan-26 17:36:56] [ info] [Backend] - Segger dll version 7.84.a loaded.
[2023-Jan-26 17:36:56] [debug] [ nRF0x0] - enum_emu_snr
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - enum_emu_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_emu
[2023-Jan-26 17:36:56] [debug] [Backend] - enum_emu_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_enum_emu_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_get_num_emus
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_emu
[2023-Jan-26 17:36:56] [debug] [ nRF0x0] - connect_to_emu_with_snr
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - connect_to_emu_with_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_emu
[2023-Jan-26 17:36:56] [debug] [Backend] - connect_to_emu_with_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_emu
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_enum_emu_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_get_num_emus
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_connect_to_emu_with_snr
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_connect_to_emu_without_snr
[2023-Jan-26 17:36:56] [ info] [Backend] - Segger logging enabled.
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Firmware: J-Link V11 compiled Dec 14 2022 09:09:01
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Firmware: J-Link V11 compiled Dec 14 2022 09:09:01
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Hardware: V11.00
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] S/N: 601008027
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] OEM: SEGGER
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Feature(s): RDI, FlashBP, FlashDL, JFlash, GDB
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] USB speed mode: High speed (480 MBit/s)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] TELNET listener socket opened on port 19021
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] WEBSRV WEBSRV_Init(): Starting webserver thread(s)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] WEBSRV Webserver running on local port 19080
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 65.390ms returns "O.K."
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_Lock()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_GetHWStatus(...)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.325ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_ExecCommand("SetRestartOnClose = 0", ...).
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.005ms returns 0x01
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_ExecCommand("DisableFlashDL", ...).
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.004ms returns 0x00
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_ExecCommand("ExcludeFlashCacheRange 0x0-0xFFFFFFFF", ...).
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.004ms returns 0x00
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_SetHookUnsecureDialog
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_SetHookUnsecureDialog(...)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.016ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_TIF_Select(JLINKARM_TIF_SWD)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 3.500ms returns 0x00
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_SetSpeed(2000)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.947ms
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_GetSN()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.006ms returns 601008027
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_load_core_data
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_ExecCommand("CORESIGHT_SetIndexAHBAPToUse = 0", ...).
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.005ms returns 0x00
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_ExecCommand("device = nRF52", ...).
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Device "NRF52" selected.
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Device "NRF52" selected.
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 10.860ms returns 0x00
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [debug] [Backend] - read_debug_port_idr
[2023-Jan-26 17:36:56] [debug] [Backend] - read_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_read_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - coresight_configure
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_Configure()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 1.105ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_select_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - Select AP 255, DP Bank 0, AP Bank 255
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.531ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x00)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Value=0x2BA01477
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.850ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.008ms
[2023-Jan-26 17:36:56] [debug] [ nRF0x0] - read_device_version
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - read_device_info
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_emu
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_IsOpen()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.006ms returns 0x01
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_Lock()
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - Just_read_device_version
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - Just_readback_status
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - Just_is_ctrl_ap_available
[2023-Jan-26 17:36:56] [debug] [Backend] - read_access_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_read_access_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_is_debug_region_powered
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_read_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_select_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - Select AP 255, DP Bank 0, AP Bank 255
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.736ms returns -1
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [Backend] - JLinkARM.dll reported "-1", an unknown error.
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_abort_debug_action
[2023-Jan-26 17:36:56] [ info] [Backend] - Attempting to clear any configuration errors in debug port before closing connection.
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x00, 0x0000001F)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.964ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.011ms
[2023-Jan-26 17:36:56] [debug] [ nRF0x0] - close_dll
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - close
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_emu
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_IsOpen()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.006ms returns 0x01
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_Lock()
[2023-Jan-26 17:36:56] [debug] [Backend] - close
[2023-Jan-26 17:36:56] [debug] [Backend] - disconnect_from_emu
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_disconnect_from_emu
[2023-Jan-26 17:36:56] [debug] [Backend] - is_connected_to_device
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_IsConnected()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.007ms returns FALSE
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_is_debug_region_powered
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_read_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_select_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - Select AP 255, DP Bank 0, AP Bank 255
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.619ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x01)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Value=0xF0000000
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.916ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [debug] [Backend] - unpower_debug_and_system_regions
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_write_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_select_debug_port_register
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x01, 0x00000000)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 1.034ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_is_debug_region_powered
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_read_debug_port_register
[2023-Jan-26 17:36:56] [debug] [Backend] - ---just_select_debug_port_register
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x01)
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] Value=0x00000000
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.684ms returns 0
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_HasError()
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] - 0.007ms
[2023-Jan-26 17:36:56] [ info] [ JLink] - [Info ] [JLink ] JLINK_Close()
[2023-Jan-26 17:36:56] [debug] [Backend] - Segger Backend closed.
[2023-Jan-26 17:36:56] [debug] [nRF520x0] - nRF family DLL closed
I've also tried to connect using J-Link Commander with no luck.
I am lost, and would like to avoid having 8 out of 10 boards dead. Any advice would be greatly appreciated.