Retiming Singer 7422 Advanced?

the machine was runing good doing lightly jobs. I only intent to change the thread in mine. and don't want to pick the under thread. Stop and all lights come on,bipper etc.
It can't pick the under thread, and when I help manually and get the under thread manually, it don't run sewing. It stuck and the case and the bobbin turns out of its cavity. Stop and turn on the lights.