Common issue on virtually all diamond cut alloys, ”worming” often starts from around the centre cap , or any stone chips. Not sure what AUC warrenty isI’m still looking for a swap for my original Black 507 alloys.
Cant advise on decat and Warrenty but if you don’t declare to your insurer they could void any claim.
Mercedes extended warranty buddy, car was only just purchased from an approved dealer in December