Hi Tim,
I am a developer working on the Registry.
When you rename a registration, the registry keeps a record of its previous names so the same name can't be quietly reused by someone else. Renaming "Tim Hubuei 01" → "Tim Banyadu 03" → back to "Tim Hubuei 01" left "Tim Banyadu 03" recorded as a former name on that registration, which is why the system treated it as already taken even though nothing is currently using it.
I've cleared that leftover entry, so "Tim Banyadu 03" is available again. You should be able to register it now. The "Tim Hubuei 01" registration is untouched and still there under its original name. (You won't need "Tim Banyadu 04" after all.)
Thanks for the clear write-up.