Boolean operations leaves messy edges

There is something strange happening. Everytime I do a boolean substract, I get very rough, messy edges, with visible yellow backfaces.

I tried to substract tube with the same tube, and got really ugly result.

And when I cut a small cube from a sphere, I got strange pits.

I tried doing it with high resolution, low resolution, but the result is always the same.

Voxel subtract is broken, fixing it for next release.