Won't let me make my name on a new account

I'm making an account and the account is made just fine, but when I try to put my name it says "An unexpected error has occurred". https://i.imgur.com/WDRn4OC.png I know the name isn't taken because if I enter a taken name it says that the name is taken. Help ;-; EDIT: I know that it's an appropriate length and it does not contain profanity.
Best New

We're testing a new feature that gives the option to view discussion comments in chronological order. Some testers have pointed out situations in which they feel a linear view could be helpful, so we'd like see how you guys make use of it.

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