Fixing a Bambu Lab X1C Error: "Extruding filament failed. The extruder might be clogged."

My 3D printer broke.

No matter what I tried, I couldn't get past this error: "Extruding filament failed. The extruder might be clogged."

I took apart the extruder gear assembly to check for clogs:

I inspected the little magnet on the filament sensor and tried flipping it around (a tip from a comment on the Bambu Labs forums):

I tried replacing the 0.4mm nozzle with a 0.6mm nozzle, but that didn't help. And I confirmed that I could manually push the filament through when the nozzle was heated.

Then I ordered a replacement gear assembly and filament sensor and waited for those to be delivered. I installed them, and still got the same error! At this point, I was starting to get a bit worried. I live in the far north of New Zealand, and New Zealand is a very small country, so we don't have many 3D printer repair specialists around. And I didn't want to have to replace my entire 3D printer, because it cost thousands of dollars. So I had no choice but to keep going and fix it myself.

I finally figured it out. For some reason, a screw on the back of the printer had become impossible to remove. It's one of the screws for the AMS internal hub unit. I had cracked that unit while trying to get the screw off, and this had caused a small bend in the PTFE tube.

Apparently, the printer is very finicky and doesn't like any extra friction during filament loading. I replaced the PTFE tube, and then the filament loaded fine! So if you encounter this error, make sure you carefully check all your PTFE tubes for kinks and replace any that are damaged.

I wish I had figured this out a bit sooner, but at least now I have a few extra spare parts for next time. My extruder unit also has some nice new replacement parts, so it should last for quite a while. I also understand the extruder a lot better now and I know how to take it apart and service it in the future.