Like with anything that moves or is under stresses there needs to be an element of tolerance, even minute, and imagine the design of these sunroof surrounds have a marginal, even micro failing in that tolerance, but as its only some and not all, maybe bad batch? inconsistent creation?
Do your journeys involve a fair amount of twisting roads? reason ask is you imagine sideways movement would create additional twisting force to this surround if oversized?
Not having really looked at one, is this just a cover/surround or is it integrated into the structure of the sunroof?
Its ok for them to replace, I would be happy to have that done and move on, but be nice to know a why also?