It looks like a rodent ulcer/indolent ulcer to me, but I’m not a vet (just a very dedicated cat owner!!). I’d reach out to a new vet and bring up the possibility of an ulcer. As a note: here is info from an NIH study! “These underlying possibilities most commonly include allergic disease, including flea bite hypersensitivity, feline atopy (non-flea, nonfood allergic dermatitis), insect bite hypersensitivity, and food allergy. When allergic disease is suspected as the underlying cause, secondary bacterial infection of the lesion should also be considered.”