RE: The server threw an exception. (Exception from HRESULT: 0x80010105 (RPC_E_SERVERFAULT))"

This looks to be a custom (out-of-process) solution (developed by XORail?) and the developer of the application should attempt to debug the issue/conditions triggering it first. e.g. Check with XORail's IT department to see what customizations exist and who could help troubleshoot. Though I may have missed something I was not able to identify or locate any Bentley code specific to "StartPDFForSingleFileComparer".

Xorail.CADAutomation.CADInterface.BentleyInterfaceBase.StartPDFForSingleFileComparer

HTH,
Bob