What this means: The job that syncs Eventbrite attendees into Salesforce stopped with an error it could not recover from, so attendees and their answers may be incomplete.

Common causes: Validation rules, triggers or flows on Eventbrite Attendee; another managed package hitting a governor limit; field-level security.

What to do: Open Maintenance for the full message. The text in brackets after "U:" shows which package or code threw the error, which is often not ours. Check Apex Jobs in Setup, fix the cause, then run a Full sync.