Are they heating the tape before installing? Cause that 3M tape should stick like crazy. If it pre-fits, I'm just at a loss on why it doesn't fit afterward, except that the installer maybe isn't doing something right. I ordered an OEM spoiler off eBay, and was worried that it wouldn't fit, given how many spoilers the installers seem to try, but it fit perfectly. I did notice that after heating the tape, (it starts to wrinkle) it stuck like crazy, and you had to get the placement perfect, and then really use your whole bodyweight to make sure it's sticking on topside and on bottom side so that there are no gaps.