Damaged PCB Heatbed  

Damaged PCB Heatbed

So I finally got into a groove with PETG printing and things had been working quite well. This particular print I had cleaned the powder-coated sheet with hot, soapy water and scrubbed it well, then finished with a final cleaning with 99% IPA.  About 30 minutes into my print I noticed a smell coming from the printer and the "front" side of my print nearest the LCD screen was starting to look almost melted.

The right models supports, if you can see them, are basically melting into a puddle and the "box" parts of the model have sagged considerably so I stopped the print here. Of course I didn't actually think to check the temp of the heatbed via my infrared thermometer. 

Here's where the real fun begins because when I removed the powder coated sheet it decided to take a chunk of the top of the PCB with it. it looks like it adhered to the powder coated sheet right at the hole in the sheet.  I've included a shot of the coating stuck to the sheet so you can see what I mean.

Now I cleaned everything up and the PETG was pretty much melted completely into the sheet and was incredibly difficult to remove without further damage, but just the front right side of the sheet. I heated the bed back up to 85C and checked various points with an infrared thermometer and everything was as expected, went up to 90C and everything was fine there as well.

Below you can see what the ends of the print are "supposed to" look like, as this was to the back of the bed and didn't seem to get overheated as the front did, which is the bottom picture looking all melted.

I really have no idea what the hell happened but it seems like something shorted or otherwise caused an intense heat spot on the bed and damaged my PCB in the process. Maybe there was some small contaminant on the underside I didn't notice but I'm not sure that would cause what I saw with the print/support melting. 

I am currently attempting to use clear nail polish over the exposed copper and will see how that holds up. I really don't want to replace my heat bed as it's quite expensive from what I understand. Also I can't find a link to actually buy one on the store.  

Any help or insight would be greatly appreciated.