See the attached spectra to see the obvious problem sensor.  I swapped the cables from the H & V sensors to the Pier Pod and the problem signal followed the cable.  So, the problem is upstream with the cable or sensor.  The HAM HEPI Horizontal L4C is certainly a pain to access:

Step1-- lock the local foot (already there on HAM1)

2 -- Disconnect the HEPI Actuator--recenter and lock up.

3 -- Remove the two Actuator mounting adapters.

4 -- Remove the L4C

5 -- Replace & Level the L4C

Reverse steps and hope you didn't move the platform enough to raise Daniel's notice (we are pretty good at not moving the system during this.)