Hello. Welcome to Just Answer.
It's possible heat that extreme has cause expansion of something, and the track is slightly misaligned now. The first thing I would try is increasing the Down Force.
If you look on the sides and the rear of the unit, you should see a knob with a down arrow, and a kG symbol next to it. I would increase the force with this knob slightly, and try the door again. I wouldn't move it more than about an eighth of a turn between attempts to close the door. Please let me know how you make out with it.