I believe I may have stumbled upon a bug concerning the autotune.
I have just performed an autotune for the pitch axis only, and the aircraft performed it successfully. However, I noticed afterwards that it changed some parameters which also affect the roll axis, namely
List item ATC_RATE_FF_ENABLE (from 0 to 1)
List item ATC_ACCEL_R_MAX (from 110000 to 0)
While the first is probably harmless (and it also concerns the pitch axis, so I admit the pitch autotune may decide to change its value), the ATC_ACCEL_R_MAX clearly only concerns the roll axis, and thus I believe the pitch autotune should not have changed its value? Furthermore, due to a bug which is already fixed in master (but not on mine, which is 3.4.2 release), the roll axis was basically turned off (ie: the drone did not perform movements in roll, neither by pilot or autopilot input). This almost caused a fly-away…
I can see the roll acceleration limiting when ATC_ACCEL_R_MAX = 0 will be fixed in the next release, but surely the pitch autotune changing the value of ATC_ACCEL_R_MAX is also a bug in itself?