This has that same feature seen ~100ms before lock loss in LSC-DARM, OMC DCPDs, and ETMX L3 master out. They all seem to be moving at the same time, so harder to differentiate, but maybe the ESD LVAMON chan, DRIVEALIGN L, and L3 master out channels start to deflect before LSC-DARM seen in attachment 2. So perhaps something with ETMX?