Firmware upgrade OTA with BL+APP

We have a device with firmware based on 14.2 (with sd-id 0x96) and we're trying to do a DFU over BLE to a firmware base on 15.2 (with sd-id 0xAE).

We can do a firmware update using segger and install the SD, BL and APP (with settings) and have it run correctly.

We can create a package with all the components and using nRF Connect on Android upload the firmware (signed with the correct key). However, this process never runs ... we just land in a situation where LED2 (on the PCA10056) ends up flashing continuously.

Checking the sd-id with a memrd, gives us the correct SD (0xAE), but all the iterations I have tried have ended up in the same place including SD+BL (no APP).