Advice on mistracking or some problem

I am having a strange problem with my turntable. First my system:

VPI Scout
Denon DL-160
Vintage Pioneer Receiver

I don't exactly know how to describe the problem other than how it sounds. There is a static/crackling sound and a fairly serious increase in volume in the left channel and dimming of sound in right channel - sound overall also is a distorted. Happens pretty randomly, but usually more at very beginning of an album. After a 20-60 seconds the sound will pop back into a normal good sound.

I am almost positive that my set-up is good. Have checked and re-checked alignment (with VPI jig) and azimuth, and I have tried various tracking weights with no predictable effect on this problem.

I can say with a very high level of confidence that it is not anything post-turntable in my system causing this. It is the turntable or the cartridge. If it's a short in the tonearm wire (which would be really bad) then it's probably not in an area where the wire is exposed as manipulation of the wire seems to have no effect, as it often does in the case of a short.

Any advice?