Single minded Foucault pendulum

I have completed a bottom driven pendulum that seems to have a preference to swing E/W. It is a 10kg bob on a 6M wire. The pivot is a tungsten carbide pin resting on a watch jewel. No matter how I start it it precesses at exactly the correct rate for 32 degrees latitude then stalls when it reaches an east/west swing. Thinking there might be some asymmetry in the drive coil's field I rotated the base but got the same result. I then tried rotating the pivot but no change. I fine tuned the charron ring and even tried without it entirely but it still settles E/W. I have also checked the area for magnets and power cables just in case. I am out of ideas! BTW it is almost exactly true E/W.

lt is a beautiful thing for the 4 or 5 hours that it works but then becomes more compass than Foucault pendulum.