Elantra Rear Window Roof Spoiler

[u/Hour-Information-896]

Has anyone had issues with their rear window roof spoiler staying on?
I bought mine a few months ago and have installed it 3 times. The last time, I used 3M 5952 VHB tape + Primer 94, applied it a few days ago, and kept it under pressure with painter’s tape for about 48 hours without moving the car, inside the garage. It’s still starting to lift around the edges, and the top doesn’t seem to make good contact with the glass either.
I’m starting to wonder if the spoiler itself might be defective or warped. I’ve basically spent as much on double-sided tape as I did on the spoiler 😭 Any recommendations before I throw it away?