This weird looking artefact showed up when I made my canvas to be Camera Space and use a Depth Only camera to render it. If I change it to Screen Space the artefacts disappear, but I need a Camera Space canvas in order to have particles nested in the UI. So my question is, what could cause this and how to fix it?
The only “solution” we came up with is to set the width and height of the Viewport Rect of the UI Camera to something like 10. So far so good but I don’t like hacky stuff like this.