This has just begun happening to me, and the printer is new. The jobs are not big – about 1 hour print time. Stops at random points during a print. On the plus side, the heaters shut off when this happens.
The printer is a Mini 1, with no LCD display or anything else on board that’s normal from this half of the decade, but it was a leftover on deep sale at Microcenter.
Possible causes would be:
the computer is going to sleep by way of a power setting timer (not the case, here)
the USB port is being disabled by way of a power setting timer (not the case here)
[*]lousy USB cable (seems to have been the problem here)
A typical cause with other printers is the USB port glitches after the print job loads, usually when the computer goes to sleep or just at random. The odd packet sends the processor off into the weeds, although any decent firmware programmer will protect against this. The way to deal with that is to disconnect the USB cable as soon as the job loads, or use an SD card, or use wifi.
This printer does not have an SD card slot, which is just weird. I now see that people seem to accept this pathetic situation, and use a Pi with Octoprint to work around it. Sounds great, but what a bummer buying a printer that wasn’t finished, and having to spend time completing it.
Of course, I tried disconnecting the USB after the print started, assuming that the job must be loaded into local memory, so there would be no way for the computer to send over a glitch. The job halted similarly to the random stoppages.
This meant that the job had not been not loaded onto the printer, but apparently requires a constant connection, which means that the job is streamed over gradually in real time.
Really? Are the designers mad? How much more would a bit of flash or RAM have cost?
I had been using the supplied USB cable, but just changed to a short one with gold plated connectors. The print went all the way for the first time out of several attempts. We’ll see about the future, but it seems likely that the USB cable that comes with the printer is crap.
Upshot: If you’re sure your computer stays up the whole time, then try a new cable.