DIAGNOSIS That awful noise is almost certainly a small rock or a super-hard, dried-up bean fragment that got caught in the burr grinder. It's a common issue with automatic machines. The grinder isn't broken, it's just jammed.
FIX First, unplug the machine. You need to get to the grinder burrs. Remove the bean hopper by twisting it counter-clockwise and lifting it off. Look down into the grinder chamber—you might see the offending piece. Use a small flashlight and a pair of long-nose pliers or tweezers to carefully extract any foreign object or rock-hard bean bit. Then, manually turn the top burr (the one that moves) with your fingers to make sure it spins freely. Reattach the hopper, plug it in, and try grinding on a coarse setting with a few fresh beans.
IF THAT DIDN'T WORK If the noise persists after clearing visible debris, a piece might have fallen deeper or a burr could be damaged. You'll need to remove the top burr assembly. With the hopper off, there's usually a plastic ring you can unscrew or tabs you depress to lift the whole burr carrier out for a more thorough inspection and cleaning.
HEADS UP Always check your beans before pouring them in. A single small stone can cause this. Also, if you leave beans in the hopper for months, the oils can go rancid and the beans can become extremely hard, increasing the chance of this happening.