I reinstalled the spoiler yesterday. I just slowly pulled back starting from the edge that was coming off while using a string to separate the tape from the trunk. It came off pretty easily. I bought 3M Super Strength Molding Tape to reinstall it. It does look better but now it looks like yours 24 hours later.
I think the spoiler might be warped. When I removed the spoiler, I cleaned it up really good and just laid the spoiler without tape on the trunk and I noticed that the spoiler was not sitting flush on the right side. There was a small gap on the right edge.
I've tried to push the spoiler in that corner to see if the adhesive in that spot would close the gap but it doesn't. It's pretty small gaps but I worry about water getting in there and possibly getting worse later or coming off in the future. I've just sent them an email as well to see about getting it removed and replaced.