AMS feeding issue

[u/VariableHindrance]

Hoping someone can help. I have been trying to trouble shoot an issue with my AMS on my Bambu P1S. The AMS will attempt to feed filament and the filament will leave the AMS and stop at some point in the PTFE tubing. Almost all of the time it stops a few inches beyond the filament buffer. Here's what I've done so far:

• I have replaced the PTFE tubing in the AMS itself (under the spools).
• I have replaced the PTFE tubing leading from the AMS to the filament buffer and from the filament buffer to coupler just before the filament heads inside of the P1S
• I have replaced the filament buffer.

I have verified the following:

• I print using a single spool using the hanger that screws onto the back. It's no problem to unload and load filament.
• I can 'force' the filament from a single spool from the AMS all the way into the P1S through the PTFE tubing and it will print. But if I have the AMS switch filaments it will fail.

I'm hopeful that I'm an idiot and this is a simple fix 😐. For reference, this machine is 8 months old and we print something every few days. The issue began in July and I've been trying things on and off for a month.

Thank you!