Wow - thanks for the detailed notes. I’m not following your solution exactly.
Do you mean you forced filament through the AMS, removed the PTFE tube at the tool head, then manually fed the filament down into the TH by setting the printer to use “external spool” while still running filament from the AMS?
Or do you mean you simply ran a print using external spool, it worked, and then went back to AMS?