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.
Sarcher, it happened with every LP and Reed/Lyra did not have any problem with rumble on any of those LPs. Anyhow, for some reasons, the rumbles all disappeared today. All I did was taken out the phono cables from Audio Tekne and and plugged it directly into my Thoeress phono instead (mainly because it was a lot faster to turn on and off and I don't have to wait as long in between while I tried to fidget with the arm/headshells etc. Go figure, don't know what is going on but will try to plug it back into AT SUT/Aesthetix later.

11flat6, not sure what you mean by teh arm properly grounded? As in the ground lead on phono cable?

Yogiboy, I do have a few test records, if the prolem recurs, I will verify it with a test record, thanks.
Hmm. I guess it's just a bad connection. I would not think that would cause woofer pumping. Could be something is causing the preamp to go into oscillation? Maybe someone with more technical background could elaborate?
Hmmm.... when I reconnected FR/Koetsu to Audio Tekne SUT/Aesthetix Io, rumble came back again :(
This is getting rather strange. I assume it means something downstream from the arm that is now the culprit. Bad tubes in Aesthetix? The sound seems fine though.
It could be tubes. I would contact Glenn at Aesthetix, and explain the issue. I'm sure he can help you figure it out.