Tbh, tessaw77 is spot on about that grinding noise being a bad sign. I had the same thing happen with my old mixer and it totally seized up after a few more uses. You really should stop using it before it gets worse.
Holy crap, grinding during heavy kneading is a really bad sign! That's not normal at all. That noise is almost always metal gears wearing down or stripping. If you keep using it like that, you will completely kill the motor. You need to stop using it right now and get it looked at.