if i’m honest: i had this problem with my previous setup (2 weeks old, the one with zram probs) and in that case the error was fixed only until next reboot, then reappeared. so (assuming it would be the same behaviour) i didn’t bother this time.
yesterday i started another new blank openhabian setup and i’ll try to understand when exactly this error begins to appear - and i’ll also give systemctl daemon-reload a try.
no, i haven’t investigated how it fills up. thanks for the advice, if the problem reappears with new setup maybe i’ll ask you how this is done 
?
for now i won’t use influxdb and i’m planning to attach my device to a UPS. i’m aware of the dataloss.
but loss of persisted data applies also to all the other services… so i’m not shure if i sould rely on zram working or if i should move it to some USB device.