Vincent told me that H1 TMSY was ringing up when the damping was on. BIO was working.

Eventually I found that I had to turn down the damping gain of all rotational modes by half, plus turn off ELF10 filters in the coil outputs, to get going stably. Since there is zero reason to go aggressive under the air, I'll leave them like that for now.

H1:SUS-TMSY_M1_DAMP_R_GAIN is -10 instead of -20.

H1:SUS-TMSY_M1_DAMP_P_GAIN is -5 instead of -10.

H1:SUS-TMSY_M1_DAMP_Y_GAIN is -5 instead of -10.

All ELF10 filters are disabled instead of enabled.

My guess is that somebody decided to go aggressive under the vacuum a long time ago, and now, in the air, OSEM positions are different and that makes coupling between DOFs different, causing oscillations.