I figured out my issue. I opened up the toolhead and found some small pieces of broken filament in the extruder gears. After cleaning the gears and installing everything back, I am able to unload without issues. I tested with both AMS. There is nothing wrong with the AMS or PTFE tubes. The culprit was the extruder gears within the toolhead. Please make sure you perform maintenance or else you will end up with this problem. I hope this information will help.
Thank you.
Gravity perhaps?
I started seeing the same issue with my Sunlu spools today. They are a bit smaller in diameter comparing to stock Bambu spools, but I didnāt have any problems until this morning when I installed a second AMS and put them both on a riser with special holding arms on the riserās sides. Appears that the entire construction is tilted a little backwards, and Sunlu spools donāt contact perfectly to the spinning rolls. I added a tiny shim underneath the back side of the AMS so it now leans a little bit forward, and this seemed to help.