I'am running the latest Stretch server version on a PiOne (Linux 4.14.65-sunxi).
I think that something is going wrong with the logrotate. The rotation is done in /var/log.hdd directory (see also the scripts in /etc/logrotate.d/).
But the original file of each is in /var/log directory and is not "cleared" after the rename, because it is not renamed.
So, if Zram copies /var/log directory to the /var/log.hdd directory, the original file in /var/log with old logging and included new logging i