Had a print fail earlier today when changing filament from one colour to the next. Got strange error messages in that it could not load filament, kept spooling in and out. I figured that this was a jam in the AMS as I had had one similar earlier so I dismantled the AMS again only to find there wasn’t a problem there.
Long story short. The failure was caused by the coupling at the rear of the body of the printer. When I pushed filament in by hand from the tube that goes to the AMS as soon as it got the the coupling it stopped, obviously hitting something. It looks like there was a slight mismatch between the hole in the tubing and the hole in the coupler.
I removed both ends and cleaned out the coupling then re-connected and all seems OK. I wish I had discovered this before I stripped down the AMS again.
I posted about how to prepare the ends of the tubing to prevent filament catching.
https://www.reddit.com/r/BambuLab/comments/14eg5bo/ptfe_tubing_tips/
This happened with my second AMS right out of the box. I trimmed the tube end coming from the print head and all was good after that.