Have you found a solution? I have the same problem since day 1.
If I put a new set of server side files, I can log on and create rooms once. As long as I don’t disconnect. If I do, I have to put a new webapps/avchat30 set to start again.
I just replicated the same pattern, but just by deleting C:\Program Files (x86)\Red5\webapps\avchat30\persistence\persistence\SHARED_OBJECT\avchat30_definst_\roomslist_v4.red5
It’s as if this file was being held after first use. Still, I can edit and delete rooms even when I can’t add...!
Hope this help.