how to make curve bevel turning evenly? I use a square curve to be the bevel. With default settings. The result is like this.

More description:
My purpose is to make a bunch of foot line all around room. I want to use poly spline type curve to achieve this.
Without bevel object the curve geometry looks like this. The cross section is twisted at the corner which causes a shrink in the middle. Any way to prevent this?

samplefile:
https://drive.google.com/file/d/1M3i4IbUPOPmV305ooXImfbh4ZBL0aU10/view?usp=sharing
Make the spine curve 2D is the key.