Over the past hour the IFO has consistently lost lock at locking ALS. As a quick test, I held in green arms manual for some time to see if the arms were having trouble holding the build up. That held fine, and the moment ALS tried to lock, there was lockloss. It appeared that the X arm was failing first.

I walked through locking ALS by hand. The failure point was ALS DIFF locking, specifically when the DARM gain is increased to 400. This seemed to kick the X arm and cause the lockloss. Leaving the IFO in down because I can't figure out what is causing this problem.