Some news,
I just ordered that on Aliexpress 
:
I am convinced that the AMS output motor is not strong enought, it is audible that as soon as the spool feeder motor stop, the AMS output motor is forcing a lot too much and filament is moving too slowly IMO (I have tested with two different AMS and three diffrent AMS output motors units), it is even more noticable with TPU filaments (also spring tensioning of this extruder is too strong for TPU, this may also explain the problem).
When unplugging the tachometer of the AMS output motor everything works better as the spool feeder motor does not stop and both motors are working together, but then problem is that the AMS get crazy and indefinitly load & unload the filament.