I'm not sure if this is a bug or something, but when starting a new project, I add some background and name some layers. Then I want to add another layer with a background below the layers I already had. So what do I do, I add the background (this case tiled background) to the layer, and move this layer all the way to the bottom of all the layers. What happens is that the tiled background is displayed behind the white layout.
I've had this many times and it's super annoying. It also shows up white when previewing the layout in browser. The tiled background was still there and you can select and move it but it's like it's gotten 'behind' the layout layer.
I'm running the latest Beta, but this also happened many versions before.