More detail later

I tried to find the source of the small squeezing instability, about 1 dB noise floor glitch every second or so. Initially I thought it was from ppol to OPO - I could see weird flashing that was quite frequent. When I was aligning ppol to the OPO I could also see higher order modes appear/disappear at about the glitch frequency. Also, I thought it would be related to ppol because the CC PLL and green controls seemed stable enough, and the homodyne spectrum shows no glitches when only IRMC is locked. 

Actually, the ppol transmission spectrum flickering disappears when the SHG is unlocked. I also now notice the same behaviour of the glitchy transmission spectrum when observing OPO transmission of only CC and only main laser. So it's maybe some stray green problem.

I tried to look in squeezing again and somehow the squeezing spectrum didn't show the glitch issue anymore, however, depending on the spectrum analyzer span, there were a lot of noise peaks. So we still have some unclear noise issues. 

Then it was time for electrical shutdown so I didn't have time to narrow down the problem further.