Microsoft Azure Recovery Service Client (MARS) won't back up the selected folders on my C: drive, but does back up other drives just fine.

Question

My MARS client won't back up the selected folders on the C: drive. It shows the following error:

Backup has encountered an irrecoverable error. Contact Microsoft Support for further assistance. (0x086C8)

The client is running on a machine in our office and not on a VM in the cloud.

I've tried updating the client and running the backup manually multiple times. The same error occurs.

I checked the event logs, and this is the details of the log that I can find (I've redacted some information that might or might not be a security risk):

- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
  <Provider Name="CloudBackup" Guid="[REDACTED]" /> 
  <EventID>10</EventID> 
  <Version>1</Version> 
  <Level>3</Level> 
  <Task>0</Task> 
  <Opcode>1</Opcode> 
  <Keywords>0x4000000000000000</Keywords> 
  <TimeCreated SystemTime="2023-06-28T06:20:11.6236999Z" /> 
  <EventRecordID>2974</EventRecordID> 
  <Correlation /> 
  <Execution ProcessID="10260" ThreadID="40812" /> 
  <Channel>CloudBackup</Channel> 
  <Computer>[REDACTED]</Computer> 
  <Security UserID="[REDACTED]" /> 
  </System>
- <EventData>
  <Data Name="StopInfo"><?xml version="1.0"?> <CBJob><JobId>b89506c2-e12b-4e27-9ed8-69326884483f</JobId><JobType>Backup</JobType><JobStatus><JobState>CompletedWithWarning</JobState><StartFileTime>133324020220713616</StartFileTime><EndFileTime>133324068116226806</EndFileTime><RecoveryPointFileTime>0</RecoveryPointFileTime><FailedFileLog></FailedFileLog><SkippedFileLog></SkippedFileLog><ErrorInfo><ErrorCode>0</ErrorCode><DetailedErrorCode>0</DetailedErrorCode><ErrorParamList/></ErrorInfo><DatasourceStatus><CBDatasourceStatus><JobState>Aborted</JobState><LastCompletedJobState>PreparingMedia</LastCompletedJobState><ErrorInfo><ErrorCode>34504</ErrorCode><DetailedErrorCode>-2137452627</DetailedErrorCode><ErrorParamList><CBErrorParam><Name>DLS_ERROR_CODE_NAME</Name><Value>34504</Value></CBErrorParam><CBErrorParam><Name>__ErrorSource__</Name><Value>Service/aibcorrupt/rbcs/Client</Value></CBErrorParam></ErrorParamList></ErrorInfo><Datasource><DataSourceId>5638840985910589048</DataSourceId><DataSourceName>C:\</DataSourceName><WriterId>00000000-0000-0000-0000-000000000000</WriterId><ApplicationId>00000000-0000-0000-0000-000000000000</ApplicationId></Datasource><ByteProgress><Total>0</Total><Changed>0</Changed><Progress>0</Progress><Failed>0</Failed></ByteProgress><FileProgress><CurrentFile></CurrentFile><Total>0</Total><Changed>0</Changed><Progress>0</Progress><Failed>0</Failed></FileProgress><PartialIcRun>false</PartialIcRun></CBDatasourceStatus><CBDatasourceStatus><JobState>Completed</JobState><LastCompletedJobState>Completed</LastCompletedJobState><ErrorInfo><ErrorCode>0</ErrorCode><DetailedErrorCode>0</DetailedErrorCode><ErrorParamList/></ErrorInfo><Datasource><DataSourceId>5638840986980785405</DataSourceId><DataSourceName>L:\</DataSourceName><WriterId>00000000-0000-0000-0000-000000000000</WriterId><ApplicationId>00000000-0000-0000-0000-000000000000</ApplicationId></Datasource><ByteProgress><Total>679863074816</Total><Changed>212992</Changed><Progress>171963904</Progress><Failed>0</Failed></ByteProgress><FileProgress><CurrentFile></CurrentFile><Total>0</Total><Changed>0</Changed><Progress>0</Progress><Failed>0</Failed></FileProgress><PartialIcRun>false</PartialIcRun></CBDatasourceStatus><CBDatasourceStatus><JobState>Completed</JobState><LastCompletedJobState>Completed</LastCompletedJobState><ErrorInfo><ErrorCode>0</ErrorCode><DetailedErrorCode>0</DetailedErrorCode><ErrorParamList/></ErrorInfo><Datasource><DataSourceId>5638840986861297797</DataSourceId><DataSourceName>N:\</DataSourceName><WriterId>00000000-0000-0000-0000-000000000000</WriterId><ApplicationId>00000000-0000-0000-0000-000000000000</ApplicationId></Datasource><ByteProgress><Total>680580628480</Total><Changed>8699904</Changed><Progress>250973696</Progress><Failed>0</Failed></ByteProgress><FileProgress><CurrentFile></CurrentFile><Total>8</Total><Changed>20</Changed><Progress>20</Progress><Failed>0</Failed></FileProgress><PartialIcRun>false</PartialIcRun></CBDatasourceStatus><CBDatasourceStatus><JobState>Completed</JobState><LastCompletedJobState>Completed</LastCompletedJobState><ErrorInfo><ErrorCode>0</ErrorCode><DetailedErrorCode>0</DetailedErrorCode><ErrorParamList/></ErrorInfo><Datasource><DataSourceId>5638840985716226361</DataSourceId><DataSourceName>O:\</DataSourceName><WriterId>00000000-0000-0000-0000-000000000000</WriterId><ApplicationId>00000000-0000-0000-0000-000000000000</ApplicationId></Datasource><ByteProgress><Total>609196507136</Total><Changed>734707712</Changed><Progress>895626752</Progress><Failed>0</Failed></ByteProgress><FileProgress><CurrentFile></CurrentFile><Total>115</Total><Changed>126</Changed><Progress>126</Progress><Failed>0</Failed></FileProgress><PartialIcRun>false</PartialIcRun></CBDatasourceStatus></DatasourceStatus></JobStatus><RecoveryPointID>0</RecoveryPointID><RecoveryType>Undefined</RecoveryType><IsRetried>false</IsRetried></CBJob></Data> 
  </EventData>
  </Event>

Sorry it's a jumbled mess.

I'm not sure what is causing the problem or why I can't seem to find any good details or support for this application.