Need help with a Toyota 860

My 860 is not sewing right. It will start sewing one or two letters then the thread jumps over the take up arm and breaks. If the thread doesn't go over the arm it wedges it self between the thread tube and the take up arm. This leads to shredding. This usually happens on the left side of the thread tube. Any idea as to what causes this?

Thanks for your help!

Doug