I've having the same issue with my Makerfarm. I have a new power supply that can deliver 24A. I have a 60mm fan on ramps. I've reset my thermistors so I know they are not shorting. I wiggle everything around just to test that and nothing fails or faults.

I get about 5-minutes into a print and it just....stops and sits. The target temps all flip to zero and everything starts to cool down. I go to my slicer and the gcode is still running away, line by line, like everything is normal. I'm using Simplify3d as my slicer. I don't think it's a slicer malfunction.

Anyone else have this issue with Ramps and Makerfarm?