User field id error for players

We’re having our first session since the new game manager went live, and my players are all experiencing the following error when trying to get through player configuration: user field _id failed provided validation rule

It won’t let them select their character to be assigned, or close the configuration.

Hi. There was a bug that caused this during the first couple of days after the user manager was introduced. If you disable and re-enable the user manager, it should fix it (by deleting those users and re-creating new ones).
I hope that helps. Let me know if you still encounter issues.