As I mentioned on Friday, I noticed a coherent shift of the HEPI platform on HAM3 as I was locking it up in preparation for ISI measurements.  Hugo gave me a window this morning so I unlocked the HEPI again and very thoroughly looked for interferences that might be pushing it out of our aligned location.  I could find no non-suspended elements touching suspended portions aside from a few of the temporarily run in-air cables.  I can't imagine that these contacts could pull the system around.
Once it was all released I pushed on the crossbeams to 'see' knocking.  I could not detect anything that looked like something running into something else but I did notice that the vertical moved fairly easily whereas horizontal motion was very stiff.  I'm trying to understand why this would be but nothing is so far revealed.  Thoughts?

For the record, based on the dial indicators, I see a CCW rotation of about 250urad caused by a shift to the east of the south side of about 0.5mm.