Did the vet ever consider it being due to syphilis? If it were syphilis, treating with baytril can affect some improvement, but once the baytril is stopped the lesions will reemerge.
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[FONT="][FONT="]Administration of the narrow spectrum antibiotic penicillin G (benzathine/procaine: 42.000 - 84.000 UI/kg, SC, IM), 4-6 repeats at intervals of 5 to 7 days, is the treatment of choice against rabbit syphilis. (Rabbits should NEVER be administered penicillin orally; it can lead to severe diarrhea).
[/FONT]Most other antibiotics will not cure the infection. Mostly, healing of the skin lesions is observed during the treatment, but relapse will occur as soon as the treatment is stopped as the Treponema cuniculi bacterium is not killed. This is particularly the case of fluoroquinolone antibiotics. Clinical signs and skin lesions develop rapidly after the treatment is stopped, often in a more severe form than before."[/FONT]
(quoted from the link I posted above)
Looking at your photos, that very well could be rabbit syphilis. It certainly looks to be presenting in the same manner. Combined with the fact that it responded to a fluoroquinolone antibiotic(baytril), but it didn't clear it up and is now coming back in even worse than before, would also suggest that this could be syphilis. Rabbit syphilis is caused by a bacteria that cannot be cured with baytril. It can really only be treated with injectable penicillin, but it will clear up completely when the correct course of pen g procaine/benzathine is given for several weeks. All this information along with photos you can compare to, is in the links that I provided previously. If it were my rabbit, syphilis would be at the top of my list as the possible cause, and that is what I would want to treat for.
If you do treat for syphilis with pen g, a few cautions. Pen g should always be injected in rabbits,
never given orally. If there is any leakage at the injection site, always clean it off thoroughly so it is not groomed off by the rabbit and ingested as this can lead to enterotoxaemia. It's always best the rabbit be eating a high hay(grass variety) diet(and confirming that the rabbit is in fact eating the hay well) with minimal pellets, as the fiber from hay helps the gut while a rabbit is on antibiotics. Giving a probiotic like bene bac may also help. It's also best to limit or better, eliminate, any high sugar/starch/carb foods, like fruit, grains, or carrots, as these can negatively affect the microflora in the gut, especially while a rabbit is on antibiotics. And at the first sign of any watery diarrhea, your vet should
immediately be contacted and treatment for enterotoxaemia (metronidazole, questran) should be started without delay as it is a fatal illness in rabbits. It's not common that it happens with injectable administration of penicillin, but it can happen in rare instances and is something to be aware of and watch out for.
http://wildpro.twycrosszoo.org/S/00dis/Bacterial/Clostridial_enteritis_rabbits.htm