Software
Bambu Studio: 1.8.4.51
OpenSCAD: 2021.01
Hardware and Filament
Bambu P1S (P1P upgraded to P1S)
extrudr PLA NX2
Preset
Generic PLA and official extrudr preset für PLA NX2
Problem
Today I was just printing with my P1S a simple box using extrudr NX2 PLA and the 0.20 Strength @BBL X1C preset from extrudr:
Then this happened 
Do you know what the hell could have been happened here?
The gobs of melted plastic normally means that print lost adhesion and started moving with the printhead. Did you have timelapse enabled?
It was not a loss of adhesion, the print was bound to the plate, no problems so far. I wonder why there are so huge blobs of melted plastic?
Timelapse unfortunately not, seems to be not supported:
Have you tried removing the SD card and pulling the file manually?
Just for thoroughness, move the model a few mm on the plate and reslice it, could be a glitch in the 3mf.
Did it happen on the same layer both times? If it did, increase the infill by 5-10% and see if the problem goes away.
The timelapse failed. It seems the issue even destroys the video, it stops when this problem begins. But fortunately I was able to record it manually:
It even happens when I use the slower default Generic PLA preset, so the profile from extrudr (which makes the print faster) is not the reason.
Just throwing it out there, have you tried a different SD card?
Either the steppers aren’t getting the power they need to move the printhead while that’s occurring, or else something is preventing that power from reaching the printhead. How to test which it is: Do you have an oscilloscope? Tap into the two coils on the steppers and see whether they are getting enough voltage and current during the peculiar event.
No, do you think it could be too slow?
Perhaps. It’s just the process of trouble shooting as the bottom seems to print without issue. The stock SD cards are known to be flaky at times.
It’s moving, just not fast enough. I’d be inclined to blame the steppers except if they were misbehaving, I think they’d be “rough”, moving in small random bursts. In the video above, the extruder appears to be moving smoothly, just not fast(ly). 
I think this is bad controller hardware. Not the signals going to the motors. Memory. In the video it looks to me like the machine is suddenly forgetting how many steps/mm it should be making and it’s doing 1 instead of 100. Or like it is scaling the entire print down by 100x without scaling the flow rate accordingly. If this was a stepper driver problem I don’t think it would be likely to effect both motors equally (unless it’s a power supply problem). This is a CoreXY machine so if one stepper misbehaves the extruder should basically be all over the place or not moving at all.
I’d expect the machine to have ECC on its memory, though. And I’d expect it to run a memory test when powered-on. If a Power Supply is bad, it should detect that, too (I mean, the printer has so many other sensors, leaving that out would be kind of inexcusable IMO). But if my expectations are valid, there should be some error being reported. Which doesn’t appear to be the case.
So either I’m wrong with my expectations of how the machine is designed, or I’m wrong with my suggesting that it’s bad memory. But I think it’s a memory error kind of problem… especially since the onset of the issue seems fairly random. It starts out OK but once the memory gets corrupted it runs incorrectly for the rest of the print.
Or maybe there’s dedicated stepper motor microcontrollers and the problem lies there, and the controller doesn’t do a memory test.
So many questions. So few answers. But this doesn’t look like the kind of problem you can fix. You have to do a ticket and send BBL a log file to review. 
One guess might be that the power supply is failing. Just for grins I checked, and according to various posts in the forum it’s the Mornsun LM100-20B24-C power supply. LOL. If true, then they’re powering your expensive 3D printer with a $20 100w power supply! 
Gee, no wonder it takes so long to warm up the heated bed. Sounds to me a bit like a heartache waiting to happen. If not now, then somewhere down the road. Does the printer contain some other power supply in addition to that one, or is that all there is?
I don’t think it is the memory, power supply or SD card, because this error is not random. It is reproducable, if I reprint it it happens again and again at the exact same spot.
I did now change the object itself a little bit and it printed without any problems:
What is your conclusion? Are you saying it was a slicer error? Or, if not, what?
BTW, nice print. Did your very first print have supports turned on? Looked like yes. I’m wondering if maybe it wasn’t completely “flat” against the build plate in your slicing of it. Or maybe a mesh error in the original model itself?
I think it must be a slicer or model glitch. My Bambu had never any similar problem.
The first failed print had supports enabled, the next failed prints did not.
It costs time and filament, but I will try a third print with the “faulty model” to find out if it is still reproducable with it.
Does your print setting has low infill%? If it does, increase the infill% by 5-10% can solve the problem. What happens is that when the infill% is low, sometimes there is one spot where the infill line is printing mid air (nothing underneath to support it, and too long a line or curve to bridge over) and from that spot the problem starts.
One can review the sliced model in the Preview tab to zero in on the few layers around the layer that the problem occured. The line or curve that’s printing mid air can be spotted.
It doesn’t always happen. The next slicing can be normal, but the one slicing after can have the problem again. So this is probably a slicing bug or at least something for Bambu Studio to improve upon.
I used the Strength preset, so there was much infill:
That’s interesting. If it were me, I would still take a look at the prevew of the few layers on the problem spot to see if there is anything that will cause the print failed.
Also when testing/trouble shooting, use the Cut tool in Bambu Studio to cut away parts and only print the portion where the problem happened. That will cut down on time and filament usage.
