We just lost lock due to a ~2 Hz yaw motion in the ASC yaw loops. This is exactly the same motion I have witnessed before, see last comment on alog 66923. This excess motion began after the HSTS damping loop change. Although our top-to-top transfer functions appeared to be fine, there might be something different about the M1-M3 transfer function, that is causing this instability. I think we need more time to characterize the changes due to these new damping loops before we reengage them. Sheila and I have reverted all PRM/PR2/SRM/SR2 damping loops, and SDFed them. Sheila has some screenshots she can comment on this alog. The "old" filters are FM6,7,8, and 9 and the correct gains should be -1 for all loops.