Zoom Integration App for Salesforce - Webinar Attendee info not populating

In addition when trying to sync an old webinar we get the following error:

Apex script unhandled exception by user/organization: 0050g0000069IwF/00D700000008zJU

Failed to process batch for class ‘zoom_app.SyncRegistrantsBatch’ for job id ‘7074u0000D7qM2R’

caused by: System.ListException: Before Insert or Upsert list must not have two identically equal elements

Class.zoom_app.SyncRegistrantsBatch.execute: line 210, column 1