You will want to call SI to confirm this, but typically the tension can be adjusted using screws at the bottom left/right of the screen to ensure even pull in all directions. This said, I still sometimes see a few waves like this that persist. In a dark room, with a standard throw projector, they basically disappear. But, it does no good with UST projectors for sure and certainly with lights on in the room, especially from the side, they will be quite visible.
But, by adjusting the tensioning at the bottom, it should get rid of these wrinkles a good deal.
Make sure you set the height of your screen before adjusting any wrinkles out.