A guy on the rolexforums reported similar issues in 2019 or 2020. His 5711 developed recurring brown spots like rust on both sides of the bracelet exactly where the pins are covered up with metal on the non-removable links. In the end he got a new watch from Patek but I am not sure they ever told him what the issue was. I haven't had any issues with mine from 2018 but maybe I just don't know as I keep using my IWC Mark XV beater for sports and swimming.
I was responding to another poster, as we were working on his account. You are totally fine -- hope your issue with this reference will be resolved in Geneva! ;-)
Thanks for your update. What’s the impression from the service center? Some sort of oxidation of white gold? Wish you a speedy turnaround of this beauty. Best, Henry
Didn’t mention it but am guessing it must have been - either that or they put the movement into an entirely new case … it really does look absolutely brand new !