Is the ability to create Telegram bots closed or a temporary error?

Question

Telegram

Wanted to create a bot. Bot name "DocBot" telegram accepted. And here username does not want to accept any. Says that this username is already taken. First, username entered a meaningful, then a simple set of letters that ends in bot.
What could be the problem? Either this is a temporary error, or all valid names are taken (which is probably not possible by 99.9999999 if you do not use some kind of "Quantum Network"))

Answer 1

Apparently the telegram does not like your "random" for the name. As for meaningful names, chances are a lot of pretty names are already taken. Tip, use a prefix for the name (I prefer to add my initials)
As for the question, everything works.

Proof