Extruder stuck half way through print

This is the 4th item I have printed, but the first one with a problem. I am printing a hollow cylinder, but only made it 40% before the printer got stuck. I didn't see it happen, but it looks like the Left extruder slipped off the edge and lowered. This caused the printed wall to get stuck between the Left and Right extruders. No more plastic was being pushed out, but the X and Y motors kept trying to move. They just kept hitting the wall, not being able to move to where they need to be. The control panel was not responsive and I had to just shut the printer down.

I am using 123D Design and Simplify3D. With the Z axis lowering mid print, does this sound like a hardware issue or software? I am printing off of the SD card that came with the printer. I checked to see if the gcode was missing part, but it has comments at the end of the file.