It seems that whilst on AC power (I STILL havent got it into the car yet, other things taking priority, mainly rust ) my Rio 2A will go into standby at random intervals.

It could be 2 minutes or 2 hours, it is very random. The unit is running around 35 degrees, with Hijack set high temp at 55.

I am running the unit from a PSU different to the factory unit, although this is rated at 1.5Amps max.
The RIO is a single drive unit running the latest consumer kernel.

Is this a power problem as I suspect, or something else?