Server crashes 'silently'?

So I’ve been using urbackup for over a year without really any issues, until I noticed last night that my laptop hadn’t been backed up since March 30th. I checked with the web frontend and I just got an Unable to reach site.

I restarted the urbackup service and it started to work again. I made a few changes to the backup schedule and the laptop client told me it was performing a backup. But then it stopped. This time I checked the disk space, memory, updated the OS and gave the backup VM a quick reboot. Same thing happened after the restart; it runs for about a minute, then just stops. After enabling the debug logging, this is the startup. Not sure if the ‘recovered frames’ points to an issue?

2021-04-08 01:21:39: Starting HTTP-Server on port 55414
2021-04-08 01:21:39: HTTP: Server started up successfully!
2021-04-08 01:21:39: SQLite: recovered 9762 frames from WAL file /var/urbackup/backup_server.db-wal code: 283
2021-04-08 01:21:40: HTTP: No available slots... starting new Worker
2021-04-08 01:21:40: WARNING: Error: Unknown action [progress]
2021-04-08 01:21:40: SQLite: recovered 252539 frames from WAL file /var/urbackup/backup_server_files.db-wal code: 283
2021-04-08 01:21:40: SQLite: recovered 12919 frames from WAL file /var/urbackup/backup_server_link_journal.db-wal code: 283
2021-04-08 01:21:41: SQLite: recovered 147579 frames from WAL file /var/urbackup/backup_server_links.db-wal code: 283
2021-04-08 01:21:41: SQLite: recovered 31 frames from WAL file /var/urbackup/backup_server_settings.db-wal code: 283
2021-04-08 01:21:41: SQLite: recovered 9762 frames from WAL file /var/urbackup/backup_server.db-wal code: 283
2021-04-08 01:21:41: SQLite: recovered 31 frames from WAL file /var/urbackup/backup_server_settings.db-wal code: 283
2021-04-08 01:21:42: SQLite: recovered 252539 frames from WAL file /var/urbackup/backup_server_files.db-wal code: 283
2021-04-08 01:21:42: SQLite: recovered 147579 frames from WAL file /var/urbackup/backup_server_links.db-wal code: 283
2021-04-08 01:21:43: SQLite: recovered 12919 frames from WAL file /var/urbackup/backup_server_link_journal.db-wal code: 283
2021-04-08 01:21:43: Started UrBackup...
2021-04-08 01:21:43: Removing temporary files...
2021-04-08 01:21:43: Recreating temporary folder...
2021-04-08 01:21:43: Testing if backup destination can handle subvolumes and snapshots...
2021-04-08 01:21:43: Backup destination cannot handle subvolumes and snapshots. Snapshots disabled.
2021-04-08 01:21:43: Testing if backup destination can handle filesystem transactions...
2021-04-08 01:21:43: Testing for hardlinks in backup destination...
2021-04-08 01:21:43: Could create hardlink at backup destination. Hardlinks enabled.
2021-04-08 01:21:43: Testing for reflinks in backup destination...
2021-04-08 01:21:43: Reflink ioctl failed. errno=95
2021-04-08 01:21:43: Could not create reflink at backup destination. Reflinks disabled. Operation not supported (code: 95)
2021-04-08 01:21:43: Binding to interface ens160 (ipv4) for broadcasting...
2021-04-08 01:21:43: Broadcasting on ipv4 interface ens160 addr 10.42.0.207
2021-04-08 01:21:43: Binding to interface ens160 (ipv6) for broadcasting...
2021-04-08 01:21:43: Broadcasting on ipv6 interface ens160 addr fe80::250:56ff:feb4:a7c4
2021-04-08 01:21:43: UrBackup Server start up complete.

After this, it seems to start working, sifting through files… then the log just stops here:

2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=44018 hash=AGRHQkMCtuibDSSQsG31Ow== target=9169963
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=192188 hash=BA6EtWkUlTEFcvU+S/D06w== target=9169964
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=38246 hash=BBFMIo22XS33+31s1r/P0Q== target=9169965
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=70249 hash=BOjgTt/UzS9jW3jRFGIA/Q== target=9169864
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=26128 hash=BWvIpXUvZSVeSQT1VvRViQ== target=9169966
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=2771 hash=BlV1lvBnMak6lv4MlbnRRw== target=9169967
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=224995 hash=Bl0XaoAB4uK5Wqf+tDy/sg== target=9169968
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=158870 hash=BnXjQeB6t4J6nXP1lKKXgA== target=9169969
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=49973 hash=BoykbGeF4nEEvsiMntvsyw== target=9169970
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=1048576 hash=CCUiqZnPzTB1yK+vAeAJkA== target=9169883
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=12225 hash=CKF0jPkAPdyzO86z7a/cEQ== target=9169973
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=65552 hash=CK4lD6jfT4uxJRDl8p2tyA== target=9170322
2021-04-08 01:23:14: LMDB: PUT clientid=5 filesize=524288 hash=CP4rwNkoxMr7pZAegRsYug== target=9169794

That’s it, after those log lines, it requires a restart. No backups are performed, no web interface…

URBackup v. 2.4.13
Running on Ubuntu 18.04.5 LTS under vCenter (ESXi) 6.5
/BACKUP has 2.4TB free, no other issues with space on the FS.

Any assistance would be appreciated.