I did solve this issue finally, Bambu was not much help. Turns out that a piece of filament broke off in the AMS unit. To fix that I had to disassemble the unit, turn it over and pull the 4 PTFE Tubes, then I pressed on the spring clamp and used a fresh piece of filament to force out the broken piece. Once I cleared that, everything worked perfecty.
Just in case anyone else encounters this…