Problem create an account on checkout

Hello,

When I let my customers create an account on the checkout page, as soon as they hit the button “Place an order” there is an error showing on top of the checkout page as you can see here: https://imgur.com/a/bAcxg

At the same time, the account is well created but the customer needs to redone the checkout a second time. I tried to find the meaning of this error but I can’t find anything about it.

Please note that I deactivate the function to create an account on the checkout page since I saw this error. And if you create an account from the login page, it is working just fine.

Do you know what does it mean and where it could come from?

Thank you