First time issue today. User since December, standard AMS with a P1S. Received a message of "failed to pull back filament from the tool head..." 

This occured during a swap between filaments in slot 4. I'm using SUNLU rolls and both rolls are with at least 800g. I have used both filaments before with no issue. The filament was "stuck" at the entry point (or so I thought) of the feeder. I pressed the lever forward, but no budging. After removing the inner portion I was able to pull the filament free. Little resistance, but freed it. 

On a second try I was using slot 2. This same error occurred but just during the first 15 min of the print prior to any filament swap. I checked and sure enough the task was just printing mid air. Got some layers down but then seemed to just not be pulling (extruder or motor issue?). Between the first and second print when I turned the printer back on, the AMS does it's usually brief load/unload process. The sound wasn't all that great. Sounded off. Not great but then it equalized back to normal. So first sign of "well something wrong still."

I cancelled this second print. I selected unload AMS in the menu and it did that without issue. Was surprised at this because I figured it'd wouldn't work at all.So at the time of the two pictures above, here is where I am: 

I was able to remove the PTFE tube from the back of the AMS enough to cut the filament and free the inner body of the AMS. Only because of this was I able to take out the AMS (otherwise too much resistance). The remaining filament btw exterior of AMS thru the buffer to the printer inlet was removed without issue (again, the unload process worked). In this section it was just "loose". There is resistance at the motor in the AMS as well as at the first stage feeder. Issue either one of these? I can remove the slot's PTFE tube with enough slack (see pic) that I could cut it and further test where the resistance is occuring (feeder or motor). Haven't done so yet. 

I have used this to test my issue. PTFE tubes are good and don't look bent (both inside and outside AMS). I don't see any broken filament.

Any thoughts? Appreciate it

AMS Motor Assist Issues?