Simple boolean difference gives weird corners

Three of the for corners are bade after a simple boolean difference. What up? V7.

Window.3dm (911.6 KB)

i think you should post the input geometry before boolean.

It is included. The Window.3dm file at the bottom.

Hello - run DivideAlongCreases > SplitAtTangents=Yes on the object.

-Pascal

Thanks Pascal. But why did that happen? Is there some setting I need to tweak?