Okay, first I verified that it is an issue on all architectures, even on
Raspberry Pi with the dedicated Raspbian armv6hf package builds.
Then I sadly found that downgrading all systemd source packages to
232-25+deb9u12 does not solve the issue. Also I wasn't able to find
another recent package upgrade which may be related, though I still
cannot believe that this issue exists for a long time, as we should have
received more reports from our users.
Is there a history of all updated packages within Debian's APT
repositories? I have no local upgrade history (apt/dpkg logs), sadly on
Stretch testing systems.
Upgrading to 241-5~bpo9+1 from Stretch backports btw solves it, though
this is not applicable in all cases, e.g. Raspbian systems where
backports are not available.
Best regards,
Micha