Originally Posted by mytwopals
Have you checked/changed the needle? Perhaps the needle is the incorrect size for the thread you are using. A needle too big or too small for the thread size can cause breakage.
Don't forget, the Grand takes a special needle (I wanna say H1-something) not one of the standard needles. There is also one way it needs to be inserted (when you insert it wrong, it breaks the thread)
Do you oil it every 2 minutes? (Seems like mine has a healthy appetite for the oil)