I agree with Deborahlees comment ---Take it back, take it back and take it back...
I posted earlier about a similar problem with my Janome. So many repairs and the problem continued. I finally said to the dealer, "don't you think it's time Janome replaces the machine?" They contacted Janome and the machine was replaced. I no longer have a problem with the bobbin spin that caused nests.
I also have a Brother that caused a tension problem in the first week. Dealer fixed it but informed Brother. Brother INSISTED I take a new machine --- WHAT SERVICE!!!!!!!!!!
You need a dealer who helps you!!!!!!!!!!!