You’re right, I switched to a development build and it went away. In terms of file types, I didn’t create the page myself, but I had a look at the folder and I can see a .woff font file, and a few .svg’s.
Edit: I had a go at making a shipping build, but it doesn’t seem like RadiantUI is working, the game runs, but there’s no HUD. Could this be to do with the fact that it’s 32-bit? Or is there some other step I need to take?