Comment # 103 on bug 1094762 from andreas bittner

No luck here. With btrfs... 776 = systemd and 791 = udev went through smoothly
and zypper dup is still ongoing but smoothly and speedily doing its business.

Theory: systemd install/restart is tied to some snapshot/btrfs or similar stuff
in a way it can not properly execute or work with nonbtrfs fs?

Only thing I can now try is to recreate the ext4 style of the situation.

If I can absolutely reproduce this bug with ext4 over and over again, that is
the path we need to follow and look for the bug.

Maybe its even some kernel or other related bug that comes into play somewhere.