Theremins help?

I have been having trouble with my Theremini suddenly just squealing one high pitch if I accidentally bump the table... so I got a mic stand for it, but the same thing happens sometimes even if it's not bumped. It's a sturdy stand but it will suddenly just switch to a high pitched squeal and now no matter how many times I recalibrate it, I can't get it back to normal.
Nothing new in the room... not wearing lots of metal... 
super frustrating....