Hi Blake,
If an Object has a Curve Modifier on it and it goes ‘beyond’ the Curve’s end points, it gets linearly extrapolated. That is what seems to be happening in your situation, therefore, I conclude that your Curve has a beginning and an end. That is not what you want here; you want a circle.
Now, I haven’t taken this Course yet, so I can’t tell how you managed this (you probably took a part of the Mesh and Converted that to a Curve), but the fix is simple:
Select the Curve and go into Edit Mode. Then in the N-Panel, check Cyclic U:

I’ll eat my hat if that doesn’t solve it. Well, I won’t actually eat my hat, that won’t do you any good, nor me. Instead I’ll see what else could be going on, so please let us know if this did the trick or not.