I always thought of han stepping on jabbas tail as a way to cover for the fact that george had planned jabba to just be a human originally. in the original footage han walks behind the human jabba without stepping on anything. but if you change him to the new jabba there is no way han could have walked around him without encountering his tail so lucas covered for that with a lame special effect of displacing the image of harrison ford that looks almost like a jump cut.

just more proof that the guy was making it up as he went.