I have only worked with Berninas in a classroom setting so I don't have any advice specifically with this machine. When I get a new machine it takes about 2 days of sewing (frustration) before we make friends. So I would say, just stick to it. But I would check ....
- Check your thread spool. Some of my thread spools have a burr at the bottom and it catches -- sometimes. Try turning it upside down or put in a new spool.
- Change the needle plate or move the needle to one side. I once had a needle nick the needle opening. It made a small burr and I had to file it down a little. You might want to take the needle plate off and look at it through a magnifying glass or try a different needle plate if you have one.
- Use the thread cutter. It's possible that the machine doesn't like the old fashioned way.
- Clean the place where the bobbin sits really well. I once had a build up of lint that was throwing off everything. When I cleaned it out, all was well.
- Do you sew at high speed? Maybe your sewing too fast and the thread doesn't have time to catch up. I would try slowing down. It may also help you to find some consistency in when it bird nests.
When my machines act up, I go back to basics. It usually turns up to be something small or I just need to go to bed and begin the next day!
Hope this helps!