When for instance a VSS backup fails you can make sure the ‘VSS Writer’ for VSS backup is running.
# Open command and type:
vssadmin list writers
# Now if you see for instance
“Microsoft Exchange Writer” Status [7]: Failed
# Now if you reset the Exchange store service the writer should and will go to Status [1] Stable.
Every writer has it’s own purpose, you should be able to figure out which of the writers is letting your backup fail.