Hi Eric, that certainly is weird!!

But it is definitely related to a control point edit - if you turn on control points for that curve, if you look in the lower right corner you can see a red square that actually shows up in the viewport:



Zooming in:




That red square is shown if you have some control points for the curve stacked up right on top of each other.

That kind of stacked up points tends to cause a problem with some of the geometry library functions that are used for determining insides and outsides of closed boundaries.

To fix it, zoom in to that area, and click and drag on that point that has the red box around it to move it slightly up and unstack those 2 points from each other so that they are distinct, then your revolve should work as you would expect.

I would like it if the geometry library was not so sensitive to stacked up points like this, but it will probably be a fairly difficult thing to make that happen anytime soon. So it is best to avoid that kind of point stacking, when you drag points and see that red box indicator, that means you have created some stacked points and you need to unstack them in that area.

- Michael