@veysel-özer thanks for the nice examples.
yeah. this is the behavior of V2. it's probably a BUG when contracting 2D geometries, as 2D geometry must have non-crossing outlines by definition.
a fix can be done in the next version. when that will happen is a big question as everything is on hold waiting for the websites to be restored.
if you have time then please create a new issue at GitHub.