Geez yes, another update.  See 18354 for past summary.

Something bad for sure for HAM2 (STS2-B) Seismometer but intermittent between very bad and poor.  See screenshot on above reference for when it is running very bad.

I moved the HAM2 instrument back over close (6') to the ITMY sensor.  And I completely swapped the cables.  That is, the HAM2 instrument is entirely on the ITMY sensor chain. and vice versa for the ITMY instrument except that there is a temp cable running from the satellite box to the interface chassis.  See attached.

I've zoomed into the coherence.  Again the Y axis is the worst, X is a little better and Z is actually very good.  Notice how the coherence between ITMY and HAM2 goes up to much higher frequency now indicating no channel wiring errors.  Also notice how the traces associated with ITMY (HAM2, red & blue) don't get to solid 1 coherence like the green trace between ITMY instrument and HAM5.  So while suttle, clearly even when only performing poorly, this sensor could be better.  The problem could be just at the sensor/cable connection but playing with that will be painful for someone, likely me.  I think it should be addressed at the shop.