I have a Nolting Pro and I think the machines are built the same way.
Change the needle,it might have a burr on it and you don't know it. Check the bobbin case and bobbin track,it might have a small burr there ,check the needleplate, again burrs.
Use the same weight thread in top and bobbin,this is important. If this doesn't work,
Call the Factory, the guys on the floor are great. They will walk you thru this and will never rush you.