Here is a fix for the problem. With this solution you only bypass the useless PMU introduced by Frsky that is not working at all. The PMU is an unknown MCU. The surface is scratched so is not recognizable.
This method just connect the MCU STM32 PIN PA8 to the mosfet that provide VMAIN, that is the power supply to the external module. With only a short cable it is fixed. I couldnt test it a lot, but for now it is working fine.
I am glad if it fix the Problem for you.
Best regards,