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!
Throwing away could be silly. Most good cart repair pros will asses its condition for free or low cost once you send it in...
Agreed solypsa, I did not take inna’s advice seriously.  I definitely plan to have it looked at when I get around to it. 
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....