I have see many people have trouble with hard disk in there car.
I’m thinking about all the vibration from the sub. ?? What happen with the small plate in the hard disk with all the vibration..
Try to put your hand on the hard disk when you play high, if you can feel some thing, you maybe have an explanation if your hard disk gone defect
The solution is to hang up your hard disk in rubbing to get less vibration to your hard disk or use a 2½ inch hard disk, it is build to handle more vibration.