Probably this. Heat from the bulbs do it.

Read up on your game, someone here should have tried it. Some you can freeze off clean, and some a lot of the paint comes with.

LTG : )

If the lifting is just visual I'd lean towards leaving it. If it affects the ball's path it's worth thinking about pulling it.

It's a big risk, plan carefully if do attempt to remove it. It's the kind of thing you can't undo once you start.

It's a big undertaking with a system 11 usually. Not worth it for a little lifting here & there

Which game, and does it effect ball travel?

I had an F14.... I got lucky with the freeze technique. I went SLOWLY.

YMMV

Good luck on your decision.

Trim off the lifting edges with exactly knife, pulling the mylar rarely turns out well

Had this happen on my Whirlwind. Debated pulling it all, ended up doing what transprtr4u suggested. Stupid sharp exacto. Cut JUST past where the bubbling was, and removed. Worked good enough for pinball.

Mylar freezes off easy. The glue remains on the PF. That is hell removing.

I always leave it. It doesn’t look that bad and you don’t notice it when focusing on playing. Plus the playfield stays protected. Seen a lot of nightmarish Mylar removal jobs that turn a decent game into a piece of junk.

I’ve debating doing this on pins where it’s lifted around an edge.

Don’t you slice up the pf tho?

Get a scrap piece of mylar or something similar and practice a little. A sharp knife or razor is important. Make a few shallow cuts rather than one deep cut, this way you don't go too deep into the paint, if at all. If you do cut into the paint, the cutline will be on the edge of the mylar, and won't show. Just don't make the cut longer than you have to.

I had Mylar lifting on a street fighter 2 that was affecting ball travel. I cut with an exacto knife and then put a new piece down. Going slow it was actually pretty easy did not cut into the playfield at all but you can see where the new piece is so not ideal if you are doing a restoration. I’m not too concerned with looks though I just like my games to play well. Playfield is nice and flat now.