Urbackup_snapshot_helper test Was Working

I have an Ubuntu 18.04 server running Urbackup v.2.4.13 using a btrfs partition for backups. All was working well with image backup file format set to Raw.

Lately, I find the server stuck in the cleanup time window. After I reboot (restarting urbackupsrv does not seem to help), backups continued. This morning I thought I would look into it and started with running urbackup_snapshot_helper test. This now fails.

I am currently running btrfsck, but what can I do to get urbackup_snapshot_helper test to pass?


Additional info: If I umount/mount that partition, the first time I run the test, it passes. If I run the test again, it will fail until I umount and re-mount the partition.