Troubles with devices on STng with e125

I have a 57' power boat with a network containing the following:

Lower Helm:
e125 (master)
e65
e7
EV-200
P70r
i50 tridata
sr150
hs5


Fly Bridge:
e125
e95
AIS 650
p70r
i70
hs5

Hardtop:
SHD 12kw open array
GPS 130

Cockpit:
a67

I'm experiencing a condition whereby at random times the STng network seems to become inaccesible to the plotters. The status icons will show No AIS, No GPS etc. The RADAR still shows as available and works fine. I'm still able to control the autopilot (which I believe is using the STng network for communications.) Previously you'd suggested testing the integrity of each STng connection to make sure they were making a good connection. I've done this as well as disconnected all the STng connections from the plotters other than the master plotter.

The only way I'm able to clear this condition is to power cycle the incoming power to the navigation network.

Any help would be appreciated.

Thanks
Ben