Strange subsonic rumble problem?

Hmm.... I have 2 arms on my TW Acoustic Raven AC, a Reed 3Q and FR 66S sitting on Minus K platform. Yesterday, I took out my Koetsu cartridge and put on Ikeda Kai on my FR 66s. After the usual setup routine, I noticed significant subsonic rumble with the woofers pumping like mad when using the FR 66s. No such problem when using Reed arm playing the same record. I never had subsonic rumble problem in my system for a long time now and no problem with FR 66s in the past. The setup seems to be fine, all the joint, screws, etc are tightened properly as far as I could tell. Overhang, VTF, VTA, etc has all been checked several times so I am out of idea now what else to check to eliminate the problem. I assume airborne vibration, acoustic feedback should not be an issue since the problem was not there before and the turntable sits in the same location for years now.
Thanks for any suggestion.