It sounds like restarting apache2 is the action that would mask var.mount,
which sounds strange.
But looking at your logs, it appears that var.mount was masked already before:
> [40367.178540] mercurio systemd[1]: logrotate.timer: Failed to queue unit startup job: Unit var.mount is masked.
When the problem is present, can you please attach the output of:
# find /run/systemd -name var\*.mount -exec ls -l {} \;
?