Sync Error: External Data Issue

I have several techs with iPads that perform syncs when they complete work. I have one tech in particular who starting last week was no longer able to sync because of the following error:
 

Quote

Last sync failed: com.prosc.sync.AbortException: com.prosc.mirror.config.server.http.MissingContainerRecordException: The MirrorSync external data source is incorrect in the offline file. Check the File->Manage->External Data Sources in the offline file and review the MirrorSync data sources.

I'm not sure why his iPad has done this. All of the other techs can sync without issue. As far as I can tell the Tech in question did not change anything on  his iPad.

Any ideas or should I just upload an Error Log?