Metallic thread is really a bummer until you find what works for you and your machine. After many years I found the answer for my machine. The metallic thread I have the best luck with is RA. I never had any luck with the kind on those little tiny spools, like Sulky. I always use a metallic needle, and I always slow down my machine when I am using metallic thread.
Don't know if you have tried these things, but maybe they will help.
I always use my RA metallic thread with a poly bobbin.