I don't have a sense of what exactly the problem is yet, but last week's adventure taught us that this 1 Hz instability is related to the gain of SRCL just as much as it is related to the DHARD, CHARD and CSOFT gains. I checked the SRCL UGF today when we reached NLN and it was at 10.5 Hz, which seems low even by these standards.

I have increased the SRCL gain by 3 dB (-7.5 to -10.5) which brings the UGF to 15 Hz.

I remeasured the MICH OLG, and it's still around 5.5 Hz, which is as Evan designed.

PRCL UGF is back to 50 Hz; we made this change in June.

Guardian and SDF updated.