SUSE OpenStack Cloud 6
Restarting crowbar with 'systemctl restart crowbar' will kill the background job and allow new backup run. Using 'crowbarctl -t 180 backup' to increase the timeout is also a valid workaround.
The database is being held by a previous task that is still processed on the server side in the background. At some point this task would have finished and new backup job would be able to run again. It is specific due to use of sqlite and plan is to move to another database.