I had a Brother 8500D, I now have the Innovis 4000D. I've had really good luck with both.
Did you register your machine when you got it? Did you call Brother customer service? They are really helpful. You can register a machine even if you purchased it used.
I think a 75/11 needle may work better. I found the 90/14 didn't work as well, the 80/12 is good but I seem to have the best results with the 75/11. I went to a seminar done by an incredible professional embroiderer and she said to use only only 40 wt. thread in both the top and the bottom so took her advice and rarely have a problem. I found my Brother machines did not like Madiera thread and the rayon sometimes shreds but maybe with a tension adjustment, that problem could be solved. I use Isacord but I've used Coats and Clark, cotton thread, serger thread, and metallics with no problem.