I am having issues printing with the ColorFabb XT filament. If first starts of very well, good flow and and nice layer placements, but after 5-8 minutes of printing, it stops flowing and the extruder starts skipping. It looks like i starts seizing up in the heatbreak. The nozzle size i use are .40 and temperature I have tried are 235 to 250 degrees. Does anyone have an idea of what I am doing utterly wrong?