I had this issue with BOTH my Brother machines (NV1000 7 innov-Is 1500d)
a few months ago.
With both machines there was a burr in the bobbin case.
After getting both machines serviced the 1500D was still giving me issues
like this. That ended up being a P.E.B.C.A.K. problem (that means me), I
had the wrong embroidery foot on the machine.