my outback had dicor on the skylights, no problems after 3 years. then I cracked the skylight by accidentally stepping on it. My Bad. used Dicor on the new skylight and haven't seen any problem so far.
Dicor has Naptha in it to soften the EPDM roof material and form a good bond. Naptha shouldn't be a problem with most plastics. What may have happened is that the skylight flange was screwed down to tight and stress cracked from thermal cycling starting at the screw holes. That's a big problem with the skylight plastic.
BTW acetone will haze, crack and damage some plastics. It can happen instantly, or it can take weeks/months before it cracks. It will solvent weld some plastics, not real good, MEK makes a better solvent weld. But still Acetone is not a good solvent to use around plastic unless you know what kind of plastic it is and if acetone will damage it.