View attachment 167395
Hear you go. Still unsure what has caused it.
It sure as hell wasn't prepsol. Unless you're cleaning your car with MEK or laquer thinners, then that looks like stress cracking to me. You're 100% sure the lights are OE? It can happen if they're moulded wrong, sealed askew, etc. It would be very rare for that to happen so severely if not a manufacturing fault. If it was in line with the headlight, I'd say excessive heat, or perhaps heat build up from a mechanic's pad being draped over it while the light is on - but it looks to be to the side.
edit - the other thing to consider is that polycarbonate lenses are coated with a urethane protective layer to shield against UV and the solvents that the dealership is touting has caused the issue. Prepsol won't remove it, though it will degrade over time (so wax/seal your headlights, peoples). If that coating had degraded to the point where it was not working, there is a very strong chance you'd have hazing or yellowing of the lens to go with it but, aside from the crazing, the lenses appear to be in fairly good condition