NRF52840 Q1AAC0 secure DFU problem

We use nRF52840-PDK (PCA10056) with MCU revision Q1AAAA. Given example of secured DFU bootloader (s140) works good. Then we changed MCU on this board to the MCU with Q1AAC0 revision, and the same example of secure DFU do not work, as also do not work other corresponding to s140 BLE examples. But applications from nRF Connect (such as BLE scanner) work fine. Surely, Softdevice version was updated in newly soldered chip. What can be the problem?