I recall others reporting issues trying to run Crossfire on UART3 on this board, regardless of the solder jumper position. It looks like this board has an inverter on UART 3, so you could also try disabling it with:
The only other thing I notice is that UART1 has DMA resources assigned, while UART3 does not. In the Ardupilot world DMA is required for CRSF, but I haven't seen (lack of) DMA resources cause any issues with CRSF on Betaflight.
Code:
resource INVERTER 3 none
save
The only other thing I notice is that UART1 has DMA resources assigned, while UART3 does not. In the Ardupilot world DMA is required for CRSF, but I haven't seen (lack of) DMA resources cause any issues with CRSF on Betaflight.