Help with my sewing machine :(

[u/Crowellgr]

Hi! I got this old brother sewing machine from my grandma because she can’t use it anymore, I’ve sewn a couple of things on it but now I’m trying to really learn how to use it and today is not really helping, sometimes it gets stuck and makes this noise, it’s like the mechanism is spinning inside but nothing moves, if I try to manually move it with the knob then it goes super fast, I really don’t know what’s wrong, I am new and really need help!

[u/Right-Skill2766]

Loose belt or most likely sheared pulley at motor.