Help! My patchbay is "squealing"

I can't seem to figure this one out. My 1/4 in. patchbay starts a high pitch squeal as soon as I patch a good number of things or particular pieces, as I've determined, and that's as much as I can figure out. For instance, I can have 6 patches made, with no squeal. Then I patch in my Yamaha Motif keyboard and what emerges is the worst high pitch squeal. If I take out the Motif, make a couple other patches, I can still have the squeal, but perhaps not as intense. It's soft enough to work for a little while, but loud enough to prevent you from tracking anything important, plus downright annoying. So what I think I know is it's not one piece of gear that keeps getting repatched. Could it be the patchbay itself? Or could there be a half-unplugged connection somewhere? I'm hoping someones else has experienced this sort of thing before.

 

Is this patchbay on the inserts and are your inserts the typical small console unbalanced single TRS type? If so, it could be the patch cables between the insert jack and the patch bay. These should NOT be made of a single twisted pair w/ shield cable. Especially if the runs between the PB and the inserts are long, you can generate a feedback loop by the inductive coupling between the send and receive wires (if the patched signal processor maintains phase). In this case you need two separate shielded cables, as in fact most of the pre-fab'd insert cables are these days.

Not sure what to make of the fact it happens when you plug in a synth. Perhaps a ground loop problem?

 

Is this an unbalanced 1/4" bay? Are the rear connections 1/4" jacks or direct solder, or some other configuration? What mixer are you using with it? The more info you give, the better we'll be able to help you.

 

It turns out the Motif is the culprit. Thanks for the input.