I use either a Babylock Jane or Juki TL98QE to FMQ and a size 16 needle. I use any kind of thread and it all works for me.

I hope you can get it to work.

As you see there are many things that can cause the thread to break. Sometimes it is just a fussy machine and it is necessary to change out your machine if you have another one, which it sounds like you do. Give this machine a break. It is good to try all the different suggestions made by others here before you retire the machine for a bit. It may just need a good rest and cleaning.