Hi,
I am currently working on an internal dfu modeled after the secure_bootloader_uart/ example in SDK 15.3.0. I have gotten the dfu to perform a successful dfu with the blinky example, but the application does not start. I have compared the output to the output of the secure_bootloader_uart_debug/ example and I find no unexpected differences. What I ended up doing to make sure that the blinky example is correct is using nrfjprog --sectorerase --program mbr_nrf52_2.4.1_mbr.hex and press the reset button and it works. This leads me to believe that some how the MBR is being disabled or needs to be reenabled, but I do not know how to do this or if this is actually the case. I checked to see if the MBR was being overwritten and that is not the case. If anyone has any ideas as to how I should go about fixing this, please let me know!