LONGER3D LK4 Pro -- Stopped Feeding Filament--Nozzle NOT Clogged

I hope this is the correct forum for my issue... I have a LONGER3D LK4 Pro that printed normally for months. And then one day I noticed the plate and print head trace the path of the object without laying down any filament. I suspected a clogged nozzle, but I can push filament thru it with no problem. Then I noticed the knurled drive wheel that feeds filament just rotates back and forth in tiny movements--it is definitely NOT drawing filament. LONGER3D.com has no support information on this topic that I can find. I have absolutely zero idea how to t'shoot this issue further. Suggestions? Recommendations?

If you've noticed the drive wheel merely oscillating, consider that the setscrew, sometimes called the grub screw has come loose. This would allow the powered shaft to spin and not provide sufficient force to move the filament. You've noted that you can force filament through the nozzle, which is a good bit for troubleshooting.

Thanks for the suggestion. I did loosen, then retighten, the two grub screws that secure the knurled drive wheel. But the effort had no effect: The back and forth movement continues. See video:

https://youtu.be/Ntb5vQwAbVQ

The video is helpful. The problem now appears to be related to the stepper driver. The board requires a specific current level to provide power sufficient to move the filament. Either the adjustment is incorrect or the stepper driver has failed. If you've been able to print before this problem appeared, the driver board may have failed.

b'woof...
And just when I need these builds. Time to contact the Chinaseum manufacturer with the issue, I suppose. Hope my chinglish is up to snuff.

If you determine that the driver has failed, it's likely to be a common component, relatively inexpensive and found on Amazon, eBay and/or Alibaba/Aliexpress.

yep i concur, either a looses connection - check the stepper lead and connectors.
Or it needs a new driver.

If you are lucky the board will use removeable drievrs, which just involves removing the faulty chip and plugging a repolacement in.
stepper drivers are just a few quid/dollars - so as with most 3d printer issues. faster and less hassle to just fix it yourself :-)

It seems the exact problem I experienced with this LK4 Pro 3D printer is rather familiar to LONGER: They made a video to t'shoot it...

https://youtu.be/XCjrieoyZ1c

I swapped the extruder and x-axis stepper cables as demonstrated and performed the respective tests--everything tested OK. I returned the cables to their appropriate connectors and ran the printer non-stop for 48hrs without a glitch. Perhaps a connection was loose; perhaps one or more male/female cable/motherboard connectors are intermittently faulty; perhaps there is a small break in one or more wires within the “E” cable (Maybe it'd be prudent to replace the cable that powers the extruder stepper motor.)

The problem seems to have disappeared... hopefully for good.

yeah loose connection most likely :-)