I looked at 2 of the locklosses from last night, (1:19am and 1:27am), and saw that for both, the DARM loop started to oscillate just before we lost lock. In the trials tonight, we were more watchful of gain peaking.
Here is the 1:19am lockloss
And here is the 1:27am lockloss
So you can see what we were doing, and what the effect was, here is a few minutes of data just before the 1:27am lockloss. The times I note below are rough, but should give you an idea of what happened at which time.
0 sec: Arms are held on resonance with ALS.
10 sec: CARM offset of 3nm added.
20 sec: PRM restored, one flash, then PRMI acquires lock.
30 sec: CARM offset reduced to 2nm, transmitted powers are about 0.1
50 sec: Transition CARM to 1/sqrt(trans) signals. Note that we are using the high gain Thorlabs PD here, so the noise is better than last Thursday.
60-110 sec: CARM offset reduction to about 1nm.
110 sec: CARM's LSC low frequency boost engaged.
120 sec: DARM transitioned to AS55Q.
170 sec: DARM's LSC low frequency boost engaged.