The bobbin is in and there is a door that closes race etc behind bobbin.
Needle sometimes hits on side other time just keeps going. The needle appears as best I can guess knocks the bobbin out. .
It was serviced before purchase from a dealer. I have used the stitches etc. but filling bobbin after put in trouble started. Not sure if it was the first fill up. Would this machine have had a metal bobbin originally and was dealer lucky plastic worked.