My uncle had a Bed Rug (outdoor carpeted bedliner) in his pickup for some years. Never a problem with it, until he moved to a new house.
He always parked the truck pointing the same direction and the same position on the driveway in front of the garage. The 2nd floor room above the garage had some very large windows and recieved direct sunshine for a good portion of the day.
His Bed Rug started to show some very strange burn marks in various spots after moving to the new house. It had been fine for 5 years before that. He couldn't figure out why it was suddenly being burned.
The Bed Rug company replaced the carpet/mat with a new one, for free, despite being more than 5 years old. Very nice of them. :)
The new Bed Rug immediately started burning too, in the same spots as the old one. :(
One day he noticed the sunlight reflected on the driveway, when the truck was not parked there. He thought about it and the lightbulb came on for him, so to speak.
He parked the truck in the usual spot on the driveway. As he suspected, the sunlight reflections in the bed of the truck matched the locations of the burns in the Bed Rug! Voila'! The cause of the problem was discovered :).
If I remember correctly, his solution was to park the truck pointing the opposite direction, on the other side of the driveway, to avoid the sunlight reflection pattern in the truck bed.