Issue pum is called with arguments

[Hans Huckebein]

Don't know wether this relates to anything already discussed under "pum is called with arguments ..." here in the forum, but

Here is what I get

Reason: 2022-03-30 02:16:56 INFO: pum is called with arguments: ['--update', '--json']
2022-03-30 02:17:05 INFO: no packages to update
2022-03-30 02:18:40 ERROR: installArchives() failed
2022-03-30 02:18:40 ERROR: Exited with returncode 1.

Infos
CPU Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz (1 core(s))
Version Plesk Obsidian v18.0.42_build1800220314.17 os_Debian 10.0
OS Debian 10.12

What I've done so far.
plesk repair all -v - okay, no problems found

Hard Disk Usage
File system
/dev/ploop20253p1
total 50 364.61 MB
used 10 251.33 MB
available 37 532.38 MB

Protected directories
/opt/psa
/var/lib/mysql
/var/www/vhosts
/var/qmail/mailnames
/var/named/run-root

What else could I possibly do?