17 hours into the lock today, we noticed that IMC-F on the wall FOM was steadily drifting off, instead of riding around 0 where it usually sits. After a bit of digging Sheila and Kiwamu found that both X and Y arm LSC tidal HEPI off load had (or had nearly) reached their limits. The limits set in the LSC model were 500 microns, while the HEPI limits are set at 700 microns, so even though the HEPIs were nowhere near out of range, the offload from LSC was being limited. This meant that LSC had to use the IMC to do the tidal control.  After some careful gymnastics Sheila was able to relieve the tidal offset from the IMC to the end station HEPIs, without breaking the lock. The limits for LSC have been updated, but this took us out of observing for ~80 minutes (23:13-0:36 UTC).

Attached plot is the last 4 hours timeseries of IMC-F, X & Y tidal mons (the offset sent to the endstation HEPIs). The first bid dip is IMC-F drifting off because the X tidal has hit it's limit, the jaggy bits are Sheila slowly ramping the offset to HEPI and letting the LSC tidal recover.