Hi Chipp - the offset mechanism in the geometry library that Moi uses has a lot of limitations in it and it gets particularly confused when you try to thicken a surface made up of multiple pieces that are not totally smooth to one another. When that happens the offsets do not themselves naturally meet up and the surfaces have to be extended in order to meet. It's that extension process that is rather prone to failure.

It would work better if you were to have a fully smooth object, like using something like Construct > Blend to build the corner piece rather than having a corner piece that is not smooth to the surrounding surfaces. Your current corner piece is only smooth at the outside edges of it, it kind of sags down a bit in the middle zone leaving a fairly sharp crease in those spots:



The offset of multiple joined surfaces with sharply meeting edges is a much more complex type of operation than an offset of pieces that are all smooth to one another, and also it's even more difficult if things are kind of relatively close to being smooth to each other because when surfaces that are nearly smooth to each other are extended it is then difficult to get a good crisp intersection between the extensions, there is sort of more like a "zone of overlapping area" rather than a crisp intersection.

So it basically does not work very well to try and offset a joined surface that has a structure like you have here with shallow meeting sharp pieces in it.

It would probably be better to build a blocky object to start with and then use filleting to put in all the round parts rather than trying to manually construct the rounded pieces.

- Michael