Issue with TELEM1 und TELEM2 when using MAVLink2HoTT adapter

Hi all,
I have experienced a weird behaviour when using the ports TELEM1 and TELEM2.
In my configuration I have an arduino mini connected at TELEM1
and a SiK radio connected at TELEM2 (see picture: )
Both have a baud rate of 57600 and both have the same SR1_ and SR2_ parameters.

Now: through the MAVLink2HoTT small program on the arduino I can see the telemetry on my MC-20 Graupner RC-Radio. As far as I start Mission Planner on my laptop and get a connection to the copter, I cannot receive the telemetry on the graupner correctly (wrong flight modi displayed, battery monitor changes continuosly, etc…)
It works very well as far I disconnect the mission planner.

It seems to me, that the ArduCopter HW doesn’t work with more than one UART interface working togheter.
Do you have the same problem?
Do you have any electric schematic of the last ArduCopter?

Many thanks.

I have a MX-20 with pixracer and ardupilot. The Mavlink2hott is connect on TELEM2 and 3DR radio on TELEM1.
Everythink was working since I update both Ardupilot and MX-20 couple days ago, bad thing to do to upgrade both in the same time.
Now 3DR is still working but no data on MavlinkHott, The MX-20 reconize the sensor but no data display in the smartbox or telemetry. I don’t know if it comes from serial TELEM2 issue or the new firmware in MX-20 2,021 is not compatible anymore with Mavlink2hott.
If one has the same firmware version and can tell me if it’s working for him
best regards