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!
Yes I think an autopsy is a good idea.

Bear in mind that if you apply a soldering iron to make sure no residual solder actually makes contact. (Gold can/will diffuse into solder although that comment applies to old-fashioned tin/lead.)

My first thought was to suspect the coil/s but I would have expected a complete O/C rather than intermittent signal. As a matter of interest does your captive tonearm cable terminate at the base of the tonearm or continue all the way to the pre-amp?
My vector 4 tonearm cable runs from the clips to the phono preamp.

Where  exactly would I put the soldering iron, on the cartridge pins and why?  Not sure I understand....
That is a bit of a scary option.  If there is an open circuit because of a bad solder connection of the wires from the coil to the pin, that might cure the problem.  But, if you apply heat too long (something pretty hard to judge) you might cause all kinds of additional damage.

I would NOT do this myself until the cartridge has been sent to an expert for examination.  If you get it back with the word that it is junk, then maybe it is worth a try.  BUT NEVER before.

Send it to SoundSmith or others that do this kind of work.  
I was adding to NoRomance’s suggestion (and your agreement to try it) a note of caution depending on the vintage of your soldering gear ;)

I personally am not proposing that you apply a soldering iron to your cartridge pins. I would suggest getting the cart checked first.

Moonglum understood and I think I agreed without thinking it thru....good idea Larry I will contact SoundSmith.