I'm trying to think of a symptom that would resemble outgassing and the only thing I can think of would be a power-related thing. Bad filter caps on the HV section.
When you put the DMD & controller into the other game, I'm assuming you didn't take the RR's PSU along with it. EPROMs also need to match games on the DMD controller for it to boot. Did you swap the EPROM out of the RR DMD controller for TSPP's Display EPROM when you tested that board?
My guess is that your DMD controller is fine, and you've got bad HV filter caps on your PSU in RR, possibly dead power transistors at this point as well. You'd need to test the HV section with a meter to confirm. I'd put money on it though.