Also, if you're getting burnt/brownish looking gunk, this usually occurs when the nozzle has plastic from previous prints stuck to it. It's good to clean your nozzle every once in a while before you start a print so you don't get any gunk on your prints
Check the communication log and see what it says when the print stops, your printer may be returning a clue as to why this is happening. If it doesn't happen in the same exact spot everytime, I would definitely say it's something with the printer and not the gcode itself
Try opening up the machine control panel (with the Rostock on and connected) send in an M106 S255 to make sure the fan turns on. This is to verify that the M106 is the right G-Code command to control the fan. If that checks out, then I would slice a model, export the G-Code and then open the G-Code ...
Makerbot style printers (flashforge) that run sailfish firmware use a binary communication protocol and not ascii based gcode like RepRap style firmware like Marlin, Repetier, etc. (your leapfrog). That's why you see different looking communication text, and this is why a lot of people like s3d. Ins...
I emailed support as Im using a modified marlin firmware provided by someone else and it uses A instead of E as well. Go to the scripts tab and in hte post processing section, use this:
{REPLACE "E" "A"}
that seems pretty cool! I would definitely use this as a visual indicator of different print stages (i.e. heating up, printing, done), wish i had a dreamer
If the problem is intermittent and sometimes a gcode file will print and sometimes the same gcode file will cause this issue, I would suspect it's a firmware issue.