Weird, I just had my 486mp tape give out on part of my bed and my PEI bowed up and ruined a very large print.
I got the PEI off easy this time by just pulling on it but it took a long time, bunch of chemicals, half a roll of paper towels and a sharp chisel to get the glue off the glass. It seems like nothing really dissolves this stuff. I tried IPA (as I hear people mention) it did not even touch it, like trying to clean off tar with water) and then I use acetone (works but very slow going, very messy and still does not seem effective on some of it), then tried orange oil (like goo gone) but was less effective than acetone and finally WD40 (hey it works on stickers) but it too did not do a lot and I went back to acetone.
Anything that really removes the sticky goo that is 3M 468mp easily? And any idea why it just randomly gave out after 4 months of use?
You need a brand new razor and a bottle of Rapid Remover. Spray that stuff on in a well ventilated area, allow to sit for a few minutes. You may have to saturate more than once. After the Rapid Remover has set for a few minutes, remove with the razor blade or several paper towels.
After a few minutes under that Rapid Remover that adhesive turns to runny snot-like consistency
As far as why it lifted, did you take any pictures when it happened of the area?
Logan has it correct. If you have to do this in the future, just remove the heat bed and put it in the freezer for an hour or so, then the PEI will pull right off of it and then the Rapid Remover works great to remove the adhesive. Then just clean with alcohol and reapply the new PEI sheet.
Here is a quick guide: https://ohai.lulzbot.com/project/mini-replacing-pei/maintenance-repairs/