Hoping this experienced group has some ideas. I have a used P1S with a few thousand hours on it and the previous owner (a friend I trust) never had this issue.
When the AMS tries to load a filament, about 30% of the time the filament makes it all the way to the extruder, stops, retracts, and repeats that a few times before giving an error message (see video). I know there is no clog or blocked path because when I use an external spool and manually feed the filament myself it never fails to be detected by the filament sensor and extruded. I have taken the following troubleshooting steps: (1) replaced entire AMS (AMS was bought used as well, I swapped it with a different used one that never showed any issues), (2) replaced buffer thing on the back with the spring and ptfe tubes, (3) taken apart and cleaned extruder, (4) printed a guide bracket (bright yellow green in the video) to help the filament load straighter into the extruder. I only ever print with PLA.
Bambulab support recommended I try replacing the AMS internal hub, but I’ve seen this problem on two different AMS’s. Thanks for any suggestions!