plesk 12.0.18 sw-engine stops without reason

I keep finding my plesk 12.0.18 sw-engine process stopped.

the sw-engine log shows nothing but a series of:


[04-Jun-2016 02:30:28] NOTICE: Terminating ...
[04-Jun-2016 02:30:28] NOTICE: exiting, bye-bye!
[06-Jun-2016 09:22:43] NOTICE: fpm is running, pid 779
[06-Jun-2016 09:22:43] NOTICE: ready to handle connections

Died at 2:30 AM.

I note that cron.daily runs at 2:30 AM, and contains the 50-plesk-daily.

I suspect it's shutting down and not restarting,

Any assistance welcome.