My Magnum 2812 inverter was doing the same thing. It was due to overheated FET's in the inverter. When the fault occurs, go to the ME remote, press the 'tech' button and use the round knob to find the 'temp' function. Rotating the knob will display battery temp, etc. and the last display is FET temp. If FET temp is 90C or above, the inverter goes to Overtemp Fault and shuts down.
If that is your issue, you can send the inverter for diagnosis and replacement of the FET board. In my case, I had the inverter replaced since I had an extended warranty that paid for all but my $200 deductible. The FET board was about $575 and that did not include shipping the thing to Magnum in Everett, WA.
Magnum has excellent tech assistance if you give them a call.
