In the afternoon shift we noticed a difficulty in locking the DRMI; once we could lock we checked the different steps, and yet again the MICH/SRCL demodulation phase had changed, especially for the 56MHz (and less so for the 169MHz); we checked a few things along the following steps:

• gains were mostly ok, we increased ASC_PR given the sidebands were lower today; both DARM and MICH had also to be increased (the former especially);
• the demodulation phase for DARM was also retuned, although to a lesser extent;
• a first check of the calibration between PD2 and PD1 for B7 was attempted, as we could see that during the swap the level of B7_DC changes; it doesn't look a lot when the change happens (CARM offset 150Hz), but it clearly escalates with the intracavity power; this was done by heart as I couldn't compute the ratio with dataDisplay (it returned a plain zero) nor did I dare to open Matlab during the shift; this will be checked again offline;
• when we managed to get to CARM Null, the PR vertical resonance at 11.6 Hz killed the lock after a while;
• later on, the acquisition up to STEP3 was quite reproducible, but we then faced issues going to CARM Null; a general lack of gains (PR, DARM, DIFFp) that we increased, but the gain of SSFS was quite high and we reduced it (again, to be better checked offline);
• what killed the lock consistently was a quick drift of the carrrier, that we could not explain so far; it happened most of the time in CARM_NULL_3F or while doing the transition to 1F. Sometime we could link it to DIFFp/WE, but not all times so this is not conclusive.