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 : Failed
# Now if you reset the Exchange store service the writer should and will go to Status  Stable.
Every writer has it’s own purpose, you should be able to figure out which of the writers is letting your backup fail.