If it happened recently, you can warm it with a hair dryer and it might stick back down.

But if it's been a while, you will have to score the Mylar at the edge of the bubble with a Xacto blade, and remove it.

What do you get when you add dirt to mud? You get more mud.

Try the hair dryer first.
Then cut it, it should prevent further lifting since you are cutting away the lifted part.
I would cut away the lifted part instead of cutting down on the playfield , that way you don't chance scoring the playfield by cutting right on top of it.

Don't do the "anchor thing"

Is this a small mylar or a big playfield covering area?

I would consider removing completely. Freeze spray, goo gone, flour, naphtha, or whatever the current popular way to remove is.
Then you can wax and redo the mylar or not.
Seems to be the swap kickout area, maybe remove the existing mylar and use a cliffy or a small spot of mylar where the ball lands coming out of the kick out

The post should have a nut under the playfield. Yes. I usually cut out areas like that. Even if it sticks back down it will likely happen again. Ive seen that a lot around posts.

Based on what I'm sseeing in the pic, I'd simply use an exacto knife and lightly score just a hair past where it's lifting, then just peel it off. Clean any glue residue on the playfield.

Dont put sharp edge of blade down towards pf. You want to cut upwards away from pf as you dont want to cut into pf. Make sure blade is new and razor sharp and be careful!

When it comes to the hair dryer technique it sounds like you'll remove the post slowly, warm up mylar, straighten/flatten mylar and put post down and dont overtighten..

ts hard to tell but was that area touched up ? looks weird . If not personally I would remove all the mylar and have a perfect like new playfield

Mylar will pucker or wrinkle or bubble under almost any post that gets installed on it. Very hard to avoid wrinkles when tightening post screws. The good news is that the size and curvature of the ball leaves a 'halo' between where the bottom of the ball contacts the playfield and the bottom of the post.

In this picture the 'halo' of wear and grime is clearly visible. The area from arrow point to arrow point is never touched by the ball. So there is no need to put mylar under posts.

Post_to_ball_gap_(resized).jpg

The following pic shows where the mylar can be safely trimmed to; that will protect what needs to be protected with the issue of post-wrinkling completely eliminated. Anywhere in the yellow zone will provide 100% protection for where the ball contacts the field.

Post_to_ball_gap2_(resized).jpg

With one caveat: over the years, the unmylared areas may discolor or fade differently that the areas sealed under the mylar.

Whole-field overlays are a different cat altogether.

It seems like you could remove the post, lift up the mylar some and trim and put down post. I would cut enough mylar so none is underneath the post and you can create that barrier. If you don't cut upwards you can cut sideways. You just don't want the blade / point to damage your playfield or another component near where the mylar will be trimmed. You also don't want to cut yourself etc..

Just take it slow and steady..

Usually on something like that I would use a retractable box blade. Click it all the way out, so it is flexible. then press the blade flat onto the field and slowly "shave off" the puckered part. I can't really tell from your pic how much has wrinkled or puckered.

If it doesn't affect the ball motion I would be tempted to just leave it alone. It doesn't look that bad in the pic.

Maybe not worth the risk. If the mylar has been down for a while, it's probably done all the peeling or whatever it's gonna do. Loosening and re-tightening anything touching the mylar may wrinkle it further.

What have you got to lose if you wait for a while? Just check on it every month and if it seems to still be progressing, trim it then. If it stays unchanged, no need to risk damage or an accidentally ugly trim line...or worse.

Be patient, Grasshopper...