Is there any debris on the bay floor that would have caused the damage? If something comes off the brushes it would still be in the bay on the floor, like rocks etc. but clearly this is not from the wash.
I always was told when something is wrong with a wash it will damage the vehicle from front to back, or all around depending on the machine. I.e. if someone tied a fishing weight to a brush it would hit the car repeatedly over and over till the wash stopped, which would damage the entire car.
Brushes do not hold debris that causes chips in paint. The customer would have also heard things hitting the car hard enough to cause chips. So when they come back days later and not at that very moment it’s a give away they didn’t hear anything wrong. So unless you have nuts and bolts on the floor of your bay that fell off your machine I would also say it’s color matching wax that was removedby the wash. Which means the paint was not “maintained” properly.
my theory is if the wash didn’t malfunction then the damage can’t be from the wash. A wash that operates properly can’t damage a vehicle that doesn’t already have preexisting damage. Yes there are SOME exceptions to that, but only a few, like windshield wipers in a tunnel, or mirror covers that aren’t folded in, also from friction washes.