Replaced tailgate around Christmas after a collision, and now noticing condensation inside a taillight. Body shop says they’re not responsible and are quoting $250 to replace. Please advice.

Edit: Thanks for all your advice. I’m going to ask my insurance if they’ll cover this as part of the original collision claim. btw, I posted the same thing to /r/mechanicadvice at the same time, and haven’t received a single reply there till now. Happy to see lemmy doing great as a reddit replacement.