Oooh! That's not good! Sure won't do your touchplate any good! That's got to be a wiring or grounding problem. Not likely anyone here can do much to help find it. You need to very carefully double-check your wiring and grounding. It is especially important that all grounds tie back to a single point. Never daisy-chain grounds! Put a voltmeter on the control input of the SSR, and see what it does when you ground the touchplate. It should be at 0V and stay there, but I think you'll see it is jumping up.
Regards,
Ray L.