I’m pretty sure it’s an impending sign of gasket failure.

The gasket breaks down and lets some coolant or oil out then after a few heat/cool cycles it reforms or moves slightly so that it seals properly again. Only a matter of time til it lets go permanently, probably when you’re halfway through a road trip in the middle of nowhere.

Fuck I wish they didn’t use these cheap shit-based gaskets all over the engine in their flagship SUV.