Over-the-air DFU requires two uploads (SDK12.0.0 + S132 3.0.0)

[Jarmo]

We made a version of bootloader_secure for our own purposes. The problem is now that application must be uploaded twice into the device (nRF52) before it really gets updated. I guess it is because of dual banking and for some reason, the bank is not changed when application is uploaded.

So I am asking if somebody knows where in the bootloader_secure is the code fragment that makes the bank changing, and what possibly goes wrong there? On the other hand, I don't find mentions of dual banking from the code (quickly peeking), so could there be some other reason for that behavior?

[Jarmo]

It does not stay in bootloader but enters into the previous version of application. Is it sure that the original example (bootloader_secure) works correctly? Because everything looks to work, It took me a while to notice that the application is truly updated only after the second upload. In the bootloader main.c there is the call nrf_bootloader_app_start(MAIN_APPLICATION_START_ADDR), is that taking dual banking into consideration?

The way I got the system finally working was to disable dual banking brutally from nrf_dfu_utils.c. What would be the correct way to set dual banking off, to use NRF_DFU_BANK_LAYOUT_SINGLE?