I agree that this looks like an Ochrolechia, maybe with eroded or abraded amphithecium. I looked at the three iNat observations that you thought were Pertusaria and yes, these are P. subambigens, a speces that characteristically makes stacked apothecia. It is also possible that your Ochrolechia is doing something similar, thought that's not typical. Lichens that have been damaged and are regrowing can have odd morphology.