For a systemd Type=fork unit 'success' is determined when the parent process exits. At this time systemd expects the PIDFile to exist. nginx actually creates the PID file in the forked process.
Presumably on single CPU systems there is a sufficient delay in scheduling for the forked process not to have created the PID file when systemd checks for it.
Bring the creation of the PID file forward into the parent process.
This may be a viable workaround.
For a systemd Type=fork unit 'success' is determined when the parent process exits. At this time systemd expects the PIDFile to exist. nginx actually creates the PID file in the forked process.
Presumably on single CPU systems there is a sufficient delay in scheduling for the forked process not to have created the PID file when systemd checks for it.
Bring the creation of the PID file forward into the parent process.