I finally got my WT150 working. I tried different temperatures for the filament I'm using. Right now I'm at 190 degrees and it seems to do the job as should be. But... There is a small bubble of filament every time the printer starts a new layer. You can see on the picture below. You see the thread and the cone are not smooth as should be.
What is the problem? Do I have to change the temperature?

quicklok.jpg