Hey everyone! Instead of creating a new topic every time someone finds a way to break CSG (This is not a small number of things, sadly), just post them here and they'll get looked at. Please make sure that you attach a model or rbxl file as an example (you can submit it as a confidential post if you'd like), and try not to submit the same thing multiple times (That said, we're aware of coplanar issues, please don't post hundreds of coplanar examples).
Stay on topic and don't post to criticize other's CSGs or CSG techniques. Posts with CSG tools are acceptable, as they can be helpful for us to debug CSG plugins or to others to find better/more consistent repros (And are just generally really awesome to look at in between failed CSGs).
This topic is for broken CSGs, including things such as: CSGs that work one way but not another, CSGs that can't separate, CSGs that create invisible/extra parts, etc. If it's something that should be doable but isn't, it goes here!