Oauth/token returning internal server error

We are using the auth0-react SDK in our application and encountering issues with the oauth/token route specifically for a user registered with a gmail account. I didn’t see any errors in the logs nor did turning off Rules & Flows resolve the issue.
The error I am getting is:

{"error":"server_error","error_description":"assert failed: expected 19 to be non-empty string"}

Attached are screenshots of the request payload.

Hey there!

Can I ask you to raise it as a GitHub issue in the SDK repo so we can work on that directly with the repo maintainers? That should be the most effective way to handle that. Once you have a link to it you can share it here so we can ping them.

The issue has been figured out. The problem was that a Pre-Registration flow was adding a user_id to the app_metadata On further reading of the documentation, this field was overwriting the actual user_id (Metadata Field Names and Data Types).
The Auth0 UI actually informs the user that user_id is not valid for app_metadata but there are no such warnings when developing Flows.
Ultimately this is an error on my part, but it would be great if there was some analysis of flows to prevent users from adding possibly dangerous app_metadata

Perfect! Thanks for sharing it with the rest of community!