I have the Brother's 1500se. until a couple years ago it worked perfectly. Now I have to get it in for service and hope it will work well when I get it back. The cost and distance to get it to the machine repair place is the hold up for me. I have this plan brewing in the back of my brain. I actually have another machine to take in and have serviced too. I can't afford to do 2 at one time.
I love the Brothers 1500se it is a great machine and for years had great success with it.
With your machine I would try one more attempted at repair. It should not be a lost cause yet. As others say, it could only be a bobbin or something else very simple. Also if you can, bring with you a sample of what it is doing. Been there and done that. Bringing that sample can make all the difference.