Tiled GPU perf. warning: Backbuffer was not cleared/discarded, doing Render.OpaqueGeometry/RenderFor

I wasn't sure if it was upgrading to 4.2 that did it, as I was sure it was working earlier today! (upgraded a couple of days ago). Having said that I have been mucking around with my dual camera set up, and scenes management.Now, it only seems to happen when an object layer is being used in both cameras. If I remove the layer from one, I don't get these errors. It also only does it when the secondary camera is set to clear "Depth Only" or "Don't Clear".Not sure if this sheds any more light on it. Very annoying though...Edit: Also, I've noticed it has something to do with the Directional light in my scene. If it's set to light the 'shared' layers, this error pops up. If I remove this layer from the light settings, the warning goes away... Very peculiar.

意思就是说多个摄像机共享一个层级，比方UI层，A摄像机显示，B摄像机也显示，就会出这个问题。