Custom udev rules and systemd services are ignored during boot, but work after boot completes

Issue

• We have udev rules to set custom user and group ownership to application disks
  These rules are working after running udevadm trigger and they adjust user and group ownership
  But after reboot we again have the default root:disk ownership

• Custom systemd services created in /etc/systemd/system do not start on boot, even though they are enabled.
  Manually starting them after boot with systemctl works