When the spool jumps it's usually because one end of the spool has a little slit in the edge to put the thread into when not sewing to keep it from unravelling. Look to make sure you have the slit away from where the thread comes off, put it on the bottom of the spindle or away from where the thread is coming off from. The thread gets caught on that slit and causes problems Hope you understand this.
Good Luck
Suzy