As suspected and reported earlier while doing coil balancing (cf logs 1 and 2), SR2 M2 UL actuation appears to be non functioning. An in-chamber cable would be disconnected.

First, in order to confirm the problem, an old range-of-motion matlab script was resurected and used : it ramps positive then negative offsets (+/- 132000 cts) to each coils of M2 stage, and looks at the motion response. The plots of the results are attached and are clearly showing a difference with the UL response, moving less than 0.1um whereas the other osems show more than 1um range of motion. 

Then, to see if the problem was in-chamber/in-air, the resistance of the four coils of middle mass was measured at the satellite box and the in-air side of the feedthru - in both cases a breakout board was used, plugging it to the sat-box side of cable H1:SUS_HAM4-31 in the first case, and the HAM4-D6-3 feedthru connector in the second case (wiring ref : D1000599). Measurements with the multimeter at the two ends roughly gave the same results described below :

LR (pins 1-14)~= 17 Ω
UR (pins 4-17) ~= 17 Ω
LL  (pins 7-20) ~= 17 Ω
UL (pins 10-23)  = ∞ Ω

The resistance of UL shows the circuit is open between the flange connector and the coil, somewhere in the chamber.

SR2 was tested by Stuart after HAM4 doors closeout and wasn't showing any actuation issues.

Since Borja balanced the coils with a non functional actuator yesterday, I will run undamped M2-M2 TFs overnight using the gain values he found, and see how the dynamic response is affected.