Just crashed two times, from logs I can only see that when I switched off AutoTune, RC2IN went to max causing copter to maximum tilt and fly off and crash. Other time when I switched autotune on RC2IN went to max causing copter to maximum tilt and fly off and crash. First time I was in ALTHOLD, second time in STABILIZE. Checked my Turnigy9X (Frsky) and no glitch on CH2 when I move CH8
This copter was flying fine, doing autotune on 3.1 with no problems.
Looks like a radio mixing problem as the value from channel 8 of 2018 is given to channel 2.
I would set channel 8 to do something else like Auto or RTL where radio input is not used and see if channel 2 follows. Maybe turning the radio off and back on to see if resets.
Did you bench check this with the copter disarmed with throttle and other things together?
That’s a weird one. There definitely is a linkage between your Ch8 and Ch2 values. I do not think the problem is in Arducopter though, as everybody would have the same problem. I really think this has to be in your radio.