It would appear to me that some where some how incompatible substances got together there and caused a reaction which softened the parent surfaces. If red RTV is the only compound you used to reinforce the parts then for some chemical reason the plastic that the parts are made of don't like RTV. If you used another compound even to clean the area that in conjunction with RTV may have caused the melt. It sure doesn't appear as though sunlight or heat caused the damage. I have had plastic (usually styrene) in contact for long periods of time with rubber and/or vinyl do the same thing. I don't believe that the dash parts are styrene but never the less it is a chemical reaction that caused your problems. May be if you tried something like JB Weld which seems to be amazing stuff, and I have never had it react negatively with mating compounds
I'm sure you're right. I've used the same set of chemicals to do this car and most others, and it's been fine; the lucite insert I think I used the red RTV.
* purple degreaser * dish-washing soap & water * sandpaper, etc * JB weld and/or PC7 epoxies * occasional superglue (bits and pieces) * SEM: vinyl prep, plastic prep, sand-free, paints * clear and black "regular" RTV.
I may or may not take it out this weekend (my new trans wasn't ready Friday; will pick up Tues or Wed) and I'll examine it.
I know I used that red RTV in a couple of small spots inside the gauges; to hold the gels onto the metal dial cards. I don't see a problem in there; there's something about the injection-mold plastic.
Also, in that bad photo, the lucite part I degreased, scrubbed with a soft brush to remove the old paint, re-painted, then carefully 1500-grit polished the raised letters; it failed in a really strange way, it looks exactly like 75-year-old paint, sort of crazed, and flaked of in shrunken flakes. Whatever happened was