I started a conversation on Questions and was told this could be an engine bug. Here’s the full detail of the issue: GUI SimpleButton overlapping issue
Simplified: I have two buttons rendered on top of each other however there’s some weird stuff happening when you rotate in/around the element. Even though in space one button is positioned in front likes:
When you view from the rear it renders like so:
I can solve this with renderingGroupId apparently but this seems like a deeper problem.
Hopefully this is a helpful bug report.