Balance bot v4.1 falls with Manual->Acro change after calibration

I have a Balance Bot which has behaved normally until accelerometers recalibration in v4.1.

After some normal runs Acro/Auto with v4.1 (video), although hearing “AHRS not healthy”, I decided to recalibrate accelerometers (which after all had been calibrated long time ago). Calibration was normal. After that, the balance bot was stable in Manual, but not in Acro: I had to start in Manual and when switching to Acro it fell immediately (bin log):

Reloading the parameters from a .param file from a previous normal Acro/Auto run didn’t change things, but going back to v4.0 both modes Acro and Manual were normal.

So now I can run it with v4.0 in Acro and Normal, but with v4.1 only in Normal (can’t try Auto yet).

It would seem that something broke at calibration or just after, but now:

  • Accelerometers and compasses calibrations are normal.
  • In v4.0 all seems to work.

What can happen?