Sorry to interfere, but I have exactly the same problem. At the moment we are taking a course on ontologies at the university. The problem occurs when trying to infer classes. I attach a link to Github where you can download the ontology. The ontology was created in Protege 5.5 environment with subsequent verification through HermiT.
I am able to reproduce the problem with your ontology. I've analyzed it, and it is caused by entity "http://www.semanticweb.org/4e6an/ontologies/2020/11/fashion#Alexander_Wang_Co." that is both a class and a named individual. The behaviour of such entities is not clear: some persons consider them as the same entity (this is known as "punning") and some others consider them as two distinct entities (usually, reasoners do that).
Owlready does not allows having entities being both class, individual and/or property.
I'm going to try to add some error message (or ignore the problem with a warning).