I have the Innovis 1500 and had lots of problems with the bobbin thread jamming and getting the upper thread underneath. After taking it in three times, the last clerk (most knowledgable - she said all Brothers can be like this), said that the bobbin needed to be wrapped differently then in the instructions (wrapping twice around the tension instead of once). That worked ok but I was still having some issues, I fixed the other issues by only using Brother bobbin thread and a bobbin genie. (But all machines have little quirks)
Good luck.