the update to v6.3.5 fails when executed in the "Settings" view and the Automatic Update at 3am (it gets stuck at installing then).

The log output is:

Aug 10 10:42:27 box:locker Acquired : box_update
Aug 10 10:42:27 box:tasks startTask - starting task 6847 with options {"timeout":72000000,"nice":15,"memoryLimit":1024}. logs at /home/yellowtent/platformdata/logs/tasks/6847.log
Aug 10 10:42:27 box:shell startTask spawn: /usr/bin/sudo -S -E /home/yellowtent/box/src/scripts/starttask.sh 6847 /home/yellowtent/platformdata/logs/tasks/6847.log 15 1024
Aug 10 10:42:27 box:shell startTask (stdout): Running as unit: box-task-6847.service
Aug 10 10:42:37 box:shell startTask (stdout): Finished with result: exit-code
processes terminated with: code=exited/status=50
runtime: 10.064s
Aug 10 10:42:37 box:shell startTask code: 50, signal: null
Aug 10 10:42:37 box:tasks startTask: 6847 completed with code 50 and signal null
Aug 10 10:42:37 box:locker Released : box_update
Aug 10 10:42:37 box:updater Update failed with error {
stack: 'BoxError: update exited with code 1 signal null\n' +
' at ChildProcess.<anonymous> (/home/yellowtent/box/src/shell.js:74:17)\n' +
' at ChildProcess.emit (events.js:315:20)\n' +
' at Process.ChildProcess._handle.onexit (internal/child_process.js:277:12)',
name: 'BoxError',
reason: 'Spawn Error',
details: {},
message: 'update exited with code 1 signal null',
code: 1,
signal: null
Aug 10 10:42:37 box:tasks startTask: 6847 done

journalctl -f output:

Aug 10 08:42:37 my.domain.com systemd[1]: box-task-6847.service: Main process exited, code=exited, status=50/n/a
Aug 10 08:42:37 my.domain.com systemd[1]: box-task-6847.service: Failed with result 'exit-code'.

I tried to reboot, update all other boxes, execute apt -f install, dpkg --configure -a, restart the box by systemctl restart box and /home/yellowtent/box/setup/start.sh, sadly nothing worked.

When executing apt -f install there was a lock problem though, but deleting the lock didn't help either:

 apt -f install
Waiting for cache lock: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 216171 (apt)      
Reading package lists... Done                                                                             
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  btrfs-progs libargon2-0 linux-image-4.15.0-147-generic linux-modules-4.15.0-147-generic linux-modules-extra-4.15.0-147-generic
Use 'apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 29 not upgraded.

What are other possible solutions?