When a user runs a Time Machine Backup from their Mac system to Apollo, sometimes an error message may pop up stating the backup disk image is already in use.
This error message indicates that some other user or computer is using the backup disk (or was using it, but didn't get disconnected properly), so Time Machine now can't access it.
Another reason that could result in this error is if the user changed the Apollo device's name after a Time Machine Backup was executed from the Mac to the Apollo.
To workaround this problem, the user should un-mount, and then re-mount the Time Machine target volume from the Apollo Utility.
Since the Apollo Time Machine Backup volume is always auto-mounted by default, users may not know it could be manually un-mounted.
To un-mount Time Machine Backup volume from Apollo:
(1) Click on the Apollo icon at the top menu bar
(2) Select and click on Turn Time Machine Automount Off
(3) After the Apollo Time Machine Backup volume is un-mounted
(4) Then select and click on Turn Time Machine Automount: On
(5) Manually start the Time Machine Backup one time and select the Apollo as a target disk.