Cartridge issues need suggestions

I am having issues with my Transfiguration Proteus - the left channel is cutting out.  It starts with a strong center  image then in a few seconds it drifts to the right intermittently, almost like someone is turning the balance control very fast.  Then it stays far right but I still have faint output in the left channel and sometimes some feedback like the stylus is out of line. 

It is not my tubes in the phono section because I checked that with my backup and it does the same thing.  I have rechecked overhang, cantilever alignment with my protractor, VTF - nothing has changed.  The only thing I haven’t adjusted is anti-skate and haven’t since initial setup.  Azimuth is set on a Basis Vector 4.  I took it off and upon visual inspection the it looks ok - the cantilever is straight but it might have shifted slightly to the left.  I can’t be sure.

Anyone had this issue - I never have...thanks for any feedback!