Can't properly unwrap a simple mesh UV distortion, apparently some scaling/dimension issue because unwrapping after making the mesh 500 times bigger fixes the problem.



That's a simple one-sided curved object (7 faces) located perfectly straight (pic. 1). So I expect UVs to be perfectly straight as well. But it gets slightly angled (pic. 2) which is critical for my tiling texture.
Making the mesh much bigger and applying the scale makes the unwrapping process behave right and expected (pic. 3)
Binary rounding errors are possible if the values used are very small or very large, or have a lot of significant figures. Blender uses 32bit floats to store values, so it is very possible to observe binary rounding errors in Blender in some cases. However I believe this is more likely because of the unwrapping algorythm used(maybe binary rounding errors are more visible when using it - I am not sure). If you try choosing Conformal instead of Angle Based this will probably solve the issue: