Boxer SBUS trainer mode broken in 2.10.6?

[r3wdi3]

I have two RM boxers, one ELRS which is the master. And one cc2500 which is the student.

This was working fine in edgetx 2.9.x, after an update to 2.10.6 on both of them, the master does not recognize the trainer input anymore.

Hardware setup:
Boxer ELRS with a radiomaster R168 receiver connected to the Jr module connector. 5v, GND and Signal/data

Boxer Cc2500 bound to that R168 receiver.

Settings on master

• serial AUX1 is set to Sbus Trainer
• trainer mode: Master/Serial
• assigned a switch to enable trainer mode

Settings on student

• nothing special, just a bind with the R168 receiver

But the sound is not played that the trainer is connected. And also the input from the student does not work anymore when the trainer switch is activated.

I have tested a Jr 4-in-1 module in the master and connected the student in FrskyX2 protocol. Then it's working but the signal drops once or twice per 10 minute flight. Not as bad as in the past when it was a real issue but it still drops.

I've also ordered a Radiomaster Ranger Micro to add elrs to the student and hooked up an ER4 receiver in sbus mode to the master Jr pins. Same issue as with the r168 receiver. The sbus trainer signal is not picked up.

Both receivers put out Sbus signal according to my Servo-tester.

I've also setup the cc2500 boxer as master with the ER4 receiver in the Jr bay. And then the ELRS boxer as student. Same issue, sbus signal is not picked up and 'trainer connected' sound is not played.

Long story short: trainer mode was working with two RM boxers, after an update to edgetx 2.10.6 it's not working anymore. I think I cross checked everything that I can crosscheck.

Any smart ideas left? Anything I forgot to check?