After all the succes of the RefCav and the PLL, we managed to restore the cavity alignement. We had to do some serious beam steering (with the ITM we steered the beam on either side and top and bottom of the ETM to centre the beam). Once we had some locking going out tdsdither script walked us to the top.

Engaging the PDH (CMB-B) servo initially it seemed to lock ok, but then the servo output started to oscillate between +/-10V. All gains seem ok (we even increased the input from -14 to -10 dB), with a 'UGF' of 11 kHz.

With this oscillation (at the limit), we were seeing the power fluctuations on the REFL_PWR_MON. I left the arm cavity unlocked, but kept the PLL going.

On another note, we did find the moment to align the WFS, so when we get the oscillaitons under control we can get the WFS going ...