I measured the power of the CC laser at various points.

According to the wiki, it should be:

325 mW at reflection of 98% beam splitter
3.3 mW at transmission of 98% beamsplitter (to fiber and PLL)
15 mW to OPO 

I set current and temperature as per the wiki (1.185 A, 38.15 C) and measured:
CC output after QWP, HWP - 320 mW
98% reflection -  59 mW
To fiber - 0.50 mW
To OPO - 3.2 mW

So it seems power levels are ~ factor 5 below nominal

I set current to 1.175 A and 1.195 A and measured again to see if it was mode hop, but got roughly the same results, slightly lower/higher respectively. 

Last time I could not see a signal from the OPO REFL PD which takes the CC error signal. This time I used a power meter to the oscilloscope, which resulted in the same thing. There is only a DC level and no reflection peaks. By contrast, the ppol transmission spectrum is fine (2V peaks as per wiki).

Perhaps it seems like the polarization is bad (before the 98% BS there is QWP -> HWP -> lens -> FI -> HWP) but I find it hard to believe that it spontaneously went to some bad polarization, without touching anything  after it was fine earlier on the day of the problem.