FDS not functional after bootloader application startup

I'm using the IoT bootloader from NRF52 SDK 14.2. When the bootloader has nothing to do and starts the main application, the FDS calls all fail in the main application. When I clear the UICR (nrfjprog -f nrf52 --eraseuicr), my main application launches (without using the bootloader) and the FDS calls work, it is only when the main application is launched through the bootloader that they fail. What am I missing?