Ender 3 - extruder stepper skipping I have a problem most likely very similar to some reported by other users: extruder stepper is visually skipping a step from time to time. It rapidly rotates in the direction opposite to the one it is supposed to rotate.
I noticed the following:

The extruder stepper jumps totally randomly - there is nothing specific in the pattern printed, position etc.
Stepper jumps more often on the infill, rarely on the walls.

Details about print:

PLA (Devil Design - various colors, they doesn't matter)
Filament guide installed on top, but not yet before the extruder (it is printing right now, I'm waiting for the ball bearings too)
Filament mounted on the top - in the place defined by Creality
Extruder is already replaced with the aluminium one
The mainboard is SKR E3 mini V2 (replaced recently)
95% flow set in Cura
Printing on glass, leveled bed (the jumping occurs on all layers, not only first)
215 °C hotend temperature, 60 °C bed temperature
Stepper motor current settings (from Marlin menu): 580 for X, Y &amp; Z, 650 for E1

Other observations:

What's interesting is that extruder motor jumps even if I manually unwind some filament, so that the only force that it has to overcome is only pushing filament into the head.
I did a quick DIY wooden spool holder, so that the filament was fed almost horizontally. This actually seemed to make things worse - stepper jumped more often. I moved spool to the top again and it reduced jumping a little.
Prints are done beatifully (after changing the motherboard, that is) - no lost lines or layers, walls connected with infill, perfect first layer etc.

What may be the cause of stepper motor jumping? How can I solve it? Does it pose a threat to the motor or stepper? I need to print filament guide and spool holder with ball bearings, so that I can minimize force required by the extruder motor, but then the stepper will probably jump during the prints. I already damaged the original mainboard because of stuck filament, I don't want to destroy another one.

This is how regular extruder retraction looks:

                
             (10 seconds)
This is how stepper skipping looks:

                
             (13 seconds)

Today I replaced the whole heat block (radiator, heater, thermistor and nozzle) to a new one (original, for now) and motor stopped skipping - at least on the calibration cube. I will see, how will it perform on more complex prints.
However, even having the prior one in hands, I couldn't find the reason, why motor was skipping - other than the fact, that I couldn't extract the bowden tube from the radiator (so maybe some filament indeed was dripping inside?)
I have a problem most likely very similar to some reported by other users: extruder stepper is visually skipping a step from time to time. It rapidly rotates in the direction opposite to the one it is supposed to rotate.

These two sentences are saying something totally different, and the latter is not what a skipped step looks like. It sounds like retraction, which is totally normal.