MavLink Problems: Sometimes I can only receive BAD_DATA packets


I have been struggling with some issues with sending/receiving mavlink packets between raspberry pi and the ground station control. In this image you can see the test procedures I did:

RF868MHz configurations:
- Serial Speed aka baudrate: 57600bps
- Air Speed: 200000bps
- EEC (golay error correction): enable
- MAVLINK framing and reporting: enable

TEST1: Conecting each RF868MHz radio to a TTL-USB converter and open a serial terminal, I was able to do a peer-to-peer conection and share dummy data between serial terminals.

TEST2: Conecting one of the RF868MHz radio to a rpi4 and the other one to the computer, I was able to do a peer-to-peer conection and share dummy data between the rpi4 and the computer again.

TEST3: Conect the Pixhawk and rpi4 using USB interface (baudrate at: 57600), I was able to make rpi4 read data from pixhawk

TEST4: Conect all the system, rp4 was able to receive data from pixhawk in mavlink
packets, unencapsulate them, send the raw data to RF868MHZ radio and then watch the raw data in computer correctly.

TEST5: Then I repeat again the TEST4 but making sure rpi4 don’t unencapsulate the mavlink packets. So in this test some times the computer can receive the data other times (a lot of times in fact) he receive BAD_DATA.

Anyone knows what is going on here? What can I do to make sure the conecting works all of the time using mavlink packets?

In the computer running the ground control and all scripts I’m using pymavlink 2.3.4.