Omnibus F4 V3 GPS not working when RC connected

I have M8N GPS (Beitian BN-880) connected to UART6 or Serial 3 on Mission Planner. I haven’t successfully got any data from GPS.

I have set:

SERIAL3_BAUD = 38 //38400

But when I disconnected PPM data. I got data from GPS.
Is there a problem when PPM connected and UART6?

I also tried to connect GPS to UART1 it works just fine.

SERIAL1_BAUD = 38 //38400

Have you soldered SBUS vs. PMM pad?

Yes I already soldered PPM pad

I have several Omnibus F4V3/F4V5 working flawlessly out of the box with arducopter. But I use SBUS only - so I can test PPM due to the lack of a receiver.

However, the numbering of the SERIAL/UART ports in arducopter is different to the silkscreen. For betaflight the both ports are RX1/TX1 and RX6/TX6. The one named RX6/TX6 on the silkscreen (the pins oriented to the processor) is SERIAL3 in AC 4.0.2.

N.B. The FC differ largely in quality…

Cut the copper between the middle pad and SBUS, so that serial port 6 and PPM can be used at the same time

i have the same problem what should i do?