Interrupted gcode commands (probably) causing print errors, failures
Greetings. I'm running a Prusa Mk2/S with the original multi material unit. Firmware 3.2.3.
I repaired fatigued bed heater and bed temperature wires two days ago, all appeared to be running fine, but print jobs now stop part way through with no error messages. The front panel shows percentage through the job, using the control knob gives the option to pause the job or stop the job, suggesting that the printer thinks that the job is still running. Bed and extruder heaters maintain temperature as if the job is still running.
Watching a job, I observed the extruder move either all the way to the side or front/back end of the bed and return, then continue the job, at random intervals, which are getting more frequent.
I hooked up the USB cable and ran Pronterface to see what diagnostics could be observed, and see messages of the form:
echo:Unknown command: "1 X128.402 Y93.415"
echo:Unknown command: "789 E.02267"
echo:Unknown command: "E.04213"
It appears that incomplete commands are being read and processed (if possible), then the remainder of a line of code is dumped. At some point, the break appears to happen at a critical point and the print head stops moving where it is.
I've reflashed the firmware (didn't seem to be relevant - 3.2.3 has been working fine since I installed it years ago), I've looked for grit/debris around the SD card slot (none), I've held the SD card in place with a rubber band to prevent potential vibrations from the machine from jostling the card in the socket. Ribbon cables don't move at all since they're separate from the bed and the extruder, all connectors to the main board and the LCD panel are seated.
(edit) Also tried different SD cards, both of which were previously reliable, same result.
Happens at different points in the code, there are no errors/spaces/strange characters in the gcode, loading the gcode back from the SD card to examine it shows that the gcode is complete, so pulling it out from the slot on the computer with Slic3r prematurely isn't the issue.
It's working just fine until it glitches, and except for being able to observe this happening with a fair bit of frequency now (a handful of events per handful of minutes), I'm unable to deliberately reproduce the trigger.
Any suggestions on what to try next, diagnostically or otherwise?
thanks
Mark