P5 tripping regular showing 'References Failed

Hi, today when sitting down to listen to some tunes, i found the P5 tripped on the above fault.
I went through to process disconnecting the incoming mains ,pulled all the out going power cords, gave it 45 minutes while i made myself a strong black coffee, and scoured this site and the net for an answer, nothing really came to light. Being and electrical engineer, i have tested out all the cables, the mains supply etc and all are ok.
The P5 sits on a Townshend 5 tier table, nothing below to cause heat.
After reconnection of all the cables and repowering, everything seemed fine, currently my Devialet’s and Kef References are packed away so not really much current is drawn, just using a small head phone rig at the moment.
After approximately 20 minutes the P5 tripped yet again.
So what’s going on?
So any advice please.

With only a headphone rig, it’s definitely not a situation of being overloaded. Also, doesn’t sound like a heat problem. One of two things I’m guessing, either a fault within the unit, or it is detecting a short circuit downstream. Good idea to check all of the cables. To test my first theory, what happens if you keep the unit on for a while with nothing plugged in? If nothing for a while, try plugging in one piece of gear so it has a load. Continue with this to try and find some kind of pattern.