Failed to pull filament - using 2 AMS units

Bambu Lab X Series Troubleshooting
1

I too often get errors saying that it failed to pull the filament from the extruder. When I go to troubleshoot, first I see if the filament is loose at the AMS, and it’s very tight. I disconnect the coupler at the back of the printer and the filament is already loose and pulls right out the back for the printer… so it’s not struck in the extruder.

Now, at this point, I am typically able to grab the filament at the AMS and pull it, but it is still tight but I can pull it out.
This AMS unit has about 7’ of PTFE tube from the AMS to the hub. Sometimes it works totally fine and I can print something with 50 color changes without issues, or sometimes It gets stuck on every change.

Not sure where there is too much friction or where it’s binding, but it’s clearly not at the head.

2

I have this problem, right now just with Bambu Yellow PLA for some reason (I have 2 AMS units with the hub). I’m not convinced this is binding, when I went to release it last night, there seemed to be a some kind of vacuum in the tube, when just releasing slightly the connector at the top rear of the printer (before it goes inside) I could have sworn I heard the sound of a tiny pressure release and at that point even with no other interactions I could hit retry and it worked. Curious…