DFU with NRF Connect (linux) write failure with unknown value (0x8005)

Hi there,
I have been trying recently to DFU a custom device using desktop nrf connect, and I get an error message as in the following picture right after pressing start DFU

I'm using Ubuntu 18.04

as you can see nRF Connect is 3.3V, debugger is PCA10056 (nRF52840 DK)

from Log; Connectivity firmware version 4.1.1, SoftDevice API version: 3. baud rate: 1000000.

nrfjprog version: 10.5.0

JLinkARM.dll version: 6.60a

I've added udev rule, so I'm assuming that DK has permission

also please note that I've tried to DFU using same everything (DK, custom board, firmware same nRF connect version) but different windows 10 setup and it did worked ok.

in the Log, there was a message not showing also, Received status with code 4 Unknown value, message: "Error sending packet to target. Code 0x802a"