I noticed this at the end of my shift yesterday, and now that the IFO has had a longer lock it has confirmed that ITMY mode 6 is slowly ringing up through the lock. These modes are right on top of each other so we have always struggled to damp them well, but we have found settings that have worked for most of O4. Whatever changes we've made with the IFO recently have made those settings not work.

I'm mainly writing this as a reminder for operators to keep an eye on these modes. Hopefully I'll find a setting that will work, but these ones are always a headache.