Microsoft Azure Backup failed to access the shadow copy because of inadequate disk space on the volume. Retry the operation after increasing the free space available in the volume (0x08174).
I have same issue while backing up. FYI i have already excluded following files from antivirus
C:\Program Files\Microsoft Azure Recovery Services Agent\bin\cbengine.exe
C:\Program Files\Microsoft Azure Recovery Services Agent\scratch\*
And I have almost 1.3 TB available space in my c drive.