Minimserver Diisappears?

[Peter@57m]

I have this router and also have problems with MininServer not always being found. See this thread https://forum.minimserver.com/showthread.php?tid=753
I tried to isolate the Virgin Superhub as much as possible by only using it in cable modem mode and use a Cisco wifi router in router only mode and have an Asus wifi router used in wifi access point mode.
From time to time I try playing around with router settings, swapping the function of the Cisco and Asus and even just running the Virgin a Superhub full function with a network switch. Nothing has ever worked - so I get frustrated and leave it.
Control points will see MinimServer on repeated starts so it doesn't stop things working but it is annoying.
I get the same behavior regardless of whether the control point is on iPad, android or PC.
I am pretty sure it's network related but it's got me beat.
NAS is a QNAP 459 Pro+