All axis "lose track" of their positions, self test fails
Started having this problem today. All the axis, but most notably the x-axis, has completely lost it's position over the bed. The values for the motors in settings is not right (values that should be high are instead low, negative values, etc). This has happened to me before, but a simple restart resolved it. I'm curious to hear whether you think this is a hardware issue or a software issue. When this happened before I believe it was due to cancelling an octoprint print via the printer's display. But this time I've unplugged the raspberry pi, done a factory reset, turned it off and on multiple times, but no luck. When attempting an auto-home or xyz calibration (hell, or the wizard, or self-test) the printhead keeps trying to go right, despite hitting the z-axis mount - I can hear and see the motors turning, trying to move the printhead to the right, almost as if the printer thought the printhead started it's journey from the far left.
This seems to be a software problem, no? If so, is it something printer related, or some bug caused by octoprint? I tried plugging the raspi back in and connecting octoprint to the printer. But when I disconnected from the octoprint ui, the octo ui was still showing on the mini's display. So I'm suspecting octopi is not disconnecting properly - but could this be the issue, considering I tried unplugging the rapi and doing a factory reset?
Or is there a problem with the motor(s), bearings, or obstructions, that's causing a physical problem which doesn't allow the printer to recalibrate itself properly again? Thinking a bit more about it, I can't remember if the previous time I had this problem was really resolved just by restarting - I have a vague memory of having to do the xyz calibration and biting my nails as it plowed into the right, before completing calibration and resolving the issue.
Even if this was a software issue, does the repeated pulling of the printhead to the right do some hardware damage?
I made a video showing the issue and explaining how I got there, etc.
RE: All axis "lose track" of their positions, self test fails
For posterity: after chatting with prusa support for a few hours the problem was finally found - the X-axis grub screw was loose. You can tighten it (at least temporarily) without dismantling the axis. See the link below.
https://help.prusa3d.com/en/article/layer-shifting_2020/#prusa-mini > Loose X/Y-axis belt pulley
One thing that was stumping me was the fact that the printhead kept smashing in to the side, but apparently that can happen if the grub screw is loose! Tightening it meant that the printhead and motors were synched, and it could complete the calibration!