I've update the BOM to include 0.9Deg NEMA17, 48mm, for the extruder drive.
The 1.8deg NEMA17 40mm, had issues with 3mm filament, slipping and under extrusion. All is good about the Ultimaker printer, except the extruder drive, even with the small diameter knurled gear, it is less than perfect.
I am using this one on my 2nd build: https://www.youmagine.com/designs/alternative-um2-feeder-version-two
Going to figure out a way to implement a gearbox drive