Minimserver unavailable - after WoL?

[timster]

I have been I putting my QNAP to sleep overnight and using WakeOnLan for a while now with no issues.
Today however, after the WoL, Minimserver remained unavailable on all control points. Minimwatch on my laptop didn't detect it either. The QNAP web App centre showed it as running, as did the Minmserver status page. Asset (also running on the QNAP) was immediately available.
I had to stop-start Minimserver from the QNAP web page.
Any reason this could have happened?