KB# - KB000809
Backup fails and Acronis log contains "invalid file reference" error.
This error is caused by file system or disk corruption.
To resolve this run chkdsk /r /f on each drive being backed up (requires reboot).
If the issue is unresolved: -
1) back up each partition individually to isolate the source of the problem
2) run Acronis Info tool (instructions here > https://kaseya.zendesk.com/entries/32393263-How-do-I-run-the-Acronis-Info-Report-Utility-) submit the output to Kaseya support along with the log sample
To access the Acronis log for a backup taken with Kaseya Backup, go to Backup tab > backup Sets function and click the success/failed link in the "Result" column.
Kaseya Backup (all versions)
Acronis Backup and Recovery