In alog 42711, I found that ETMX ISI St2 is moving a lot more than the other BSCs. I suspect this is probably some mechanical rubbing somewhere, so I've been looking for ways to mitigate the loss of performance. Turning on the ST2 RX/RY isolation (high gain, dc coupled, with 750mhz cps/gs13 blends) loops helps a lot. We typically leave these off because they inject GS13 noise into the X/Y dofs, but for this chamber it seems to be an improvement over a large frequency band in both the rotational and translation dofs. Attached image is for RY & X, but RX & Y is simlar. The dashed lines are with the loops rotational loops off, solid lines are with them on, green is the X gs13 signal, brown is the RY. Most interesting is the big lump around 50mhz that goes away when the loops are engaged, I guess the "rubbing" is causing extra RY, X sees that *g/w^2 and closing the cps loop suppresses that extra motion? The motion, especially ~10-30hz is still than the other chambers, but turning these loops on makes the motion below ~5hz down to 30mhz mostly better.