Removing baked-on plastic film from metal roof panels

I haven't been on here in years, but I "re-discovered" the forum from an RCS email this morning. Nice to see a couple familiar faces still here! As luck would have it, I came across a problem this afternoon that I don't have a solution for, and thought maybe someone on here would have an idea.

I am installing a radius metal roof for a customer who had another roofer lined up for her job, but after months of putting her off he finally admitted he didn't know how to do it. They did install some regular metal panels for her, but they never removed the plastic film from the panels, and it has now been baked on by months of Florida sun. Some areas will peel, but most of it is so stuck that you cant even get it started. Has anyone had to deal with this before and what did you find that did or didn't work? (The metal is painted galvalume)