LHO control room crew-

We suspect that something about the output Faraday has changed. 

• One observation is that the powers in HAM6 dropped 5% in Monday night's lock (see first attachment). 
• We spent a lot of time in SRY and single bounce, and comparing today's single bounce times to times Jennie Wright found from the last few weeks ago 77204.  Jenne Driggers was able to restore the same throughput from input power to HAM6 powers in single bounce by moving SR3 and SR2 by 800 urads in yaw, 77388.  We checked many witness sensors for large alignment shifts, it doesn't seem that any suspension shifted enough to explain this.
• We then tried to reproduce a SQZ single bounce from 2 weeks ago OMC scans, by reseting all PSAMs and osems on ZM4/5/6 SRM, and OM1/2.  This resulted in much lower power on AS_A and AS_B than two weeks ago, indicating that something is also shifting this beam.  We were able to restore the power by moving in alignment into the OFI by ~200 urad in yaw or pitch of ZM5.

The only thing that seems common to these two is the OFI, a baffle in it's vicinity or something like a wire from the fast shutter impacting the beam on the way to OM1.  We'd actuated the fast shutter and see no change in the AS camera, so we don't think that the fast shutter is the issue, which points us to looking at the OFI.

Editing to add that Keita points out something like a bad spot on OM1 is also a possibility.