Hello, I'm having an issue with a solid swept cut producing what I believe is incorrect geometry.I've made a basic part that isolates the issue I'm having on a more confidential part.

Above  is my setup, a simple vertical cylinder moving on a diagonal downward path.

And this is the result. As expected the vertical wall is straight, but the trailing edge of the cylinder make the bottom edge curved (probably an ellipse).

This is the result when changing the angle from 30° to 20°. As expected, the curve is flatter but still there.

At 9.8° it's flatter still.

But at 9.7° the bottom edge suddenly changes into a flat. I did a convert entities on the edge and it is truly a line, no curve at all. This makes no sense to me geometrically, I can't think of a reason why that edge would every be straight, it should only approach straight. Am I missing something, or is SW giving me inaccurate geometry? And if so, how do I remedy this? As you might have guessed, the cylinder represents a CNC mill on a high precision part, and I need to know what geometry I'm really getting from my mfg process. I've attached the SW file for you to experiment with if it helps. Thank you in advance for any help you can give.