Strange issue with TT Rumble on VPI Prime

[gadawg]

Hoping someone could shed some light on what might be going on. I am getting TT rumble from my VPI Prime with a Soundsmith Zephyr cartridge after about 2 years of playing just fine. Its beginning to happen when I turn the volume up a bit but again didn't do this until recently. I did change the Pre but the noise floor is lower on the new pre. Here's the kicker ... it only does it on the first 1/5 of the record. Once it gets approx. 1/5 into the side I can turn it up as loud as I want with zero rumble. Not any at all! Very strange. Hoping anyone can provide a suggestion. Since it doesn't happen but at the beginning I don't think its feedback causing it and to be clear its the woofer pumping type of rumble that is probably in the 7-12 hz region. I used to have a hum problem but put it on an HRS platform and that was that for the hum. Could this be a bearing issue? And it does it on every record.

Call me curious George! :-)