Well @work we succeded to print NinjaFlex with Ultimaker3 ... see pics below
best settings :
nozzle : 230°c
bed : 50°c
extrusion : 106%
speed : 15 mm/s (initial layer 10mm/s)
no retractation
for small items, use Brim 9mm
also use fine lube on the filament before entering the bowden !!! very important !!
that's it guys