If it was hot enough to melt that, make sure you're checking the rack temps with a temp gun before anything else. That shouldn't be able to happen.
I actually picked up an AP rack second hand where the tape burned a hole through the tub on the bottom. I don't know if it was a similar issue or not... just how I got it. The old heat tape was still in it and it had one single nasty burn spot. The rest of the tape seemed fine, but I didn't risk keeping it.
Yes! I was thinking this sounded dangerous too- maybe the tape is (or became) defective.
Rudeness is the weak man's imitation of strength. Eric Hoffer(1902 - 1983)
“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” ~ Gandhi