They will not necessarily fix it under warranty if someone else installed your spoiler other than the dealership's paint & body shop.
And yes...I have had to adjust my deck lid. My dealership installed it wrong after they installed my Havoc rear spoiler. Because it was to tight...it rubbed all the paint off underneath the deck lid. So I adjusted it myself when the dealership said they couldn't do anything about it. There are screws on the hinges that can be loosened to allow some movement and then retightened once it's adjusted properly.