When running Office 365 backup, the backup sets may fail or stuck with no errors.

Enabling debugging on the Windows DS-Client may report the following error in the debug log.

5440/18-11-21,16:46:25 special_set\Cloud\Office365\Office365Backup.cpp 1046 ERROR: empty ACL for the item: C:\BUFFER_asigra\buf\22\1\

5440/18-11-21,16:46:25    special_set\Cloud\Office365\ExchangeOnline\ExchangeOnlineDownloadManager.cpp    236    CExchangeOnlineDownloadManager::populateRequestQueueUnlocked() add     C:\BUFFER_asigra\buf\22\1\\\


This error message means that the "Use buffer" option was enabled in the backup set properties which is not support for any of the Office 365 backup sets.


Go through the Office 365 backup sets and remove the check mark from option, "Use Buffer".