random print jam/screw up

so i came home to my extruder making a horrendous noise and the x axis all the way home with plastic just dumping out, repetier shows it stuck at printing a layer no errors, this is the second time this has happened an im affraid it might cook something if it happens again no idea whats wrong any thoughts?

prusa i2
repetier firmware and host

Is there a G28 (home all axes) at the beginning of your gcode? Is it possible that the printer isn't exactly homed at the beginning of the print and the x carriage bumps into the endstop switch during the print? Maybe it's missing steps during the print causing the controller to not know the actual position of the x carriage (causing it to eventually bump into the endstop switch). Does the part that managed to print before it failed look okay or does it look like steps (or entire moves) were missed? After the failure, does anything move other than the extruder? Does filament get chewed up by your hobbed bolt? I don't see why the extruder would be making any different noises just because it's extruding into mid air, are you sure the noise is coming from the extruder?

no it has homing, it goes great then goes all the way home and the extruder just keeps runing at max feedrate and dumps filament its only ever happened twice and its running perfect now i trippled check all my connections and they are perfect, infact they are entirely overkill there are two heavy gauge gnds soldered on the board an extra jumper from there to the bed mosfet which is a heavy duty 70 amp i believe is what botronics supplied, and two heavy positve wire soldered on the board with another solders heavy wire to the bed with a direct connection to the positive of the power supply, all axis move great by manual, but i did get a checksum error in the last print so it leads me to believe its software related.

Went back and check my fan with a multimeter because it dirs and found 15v i fixed the psu and reflashed the bootloader and the sketch now just gotta do a test print