I have an Asus R9 390. using Windows 10. It's a new system with a fresh install of windows and the latest Radeon drivers. I was playing Portal 2 today and I am seeing some very undesirable glitches with what appear to be reflection maps.
I have attached screenshots. The second file (2015-12-25) is what I am seeing in game. The first is from a Youtube walk through of the same area to illustrate clearly how the rendering is messed up.
Anyone heard of this problem before? I have only seen it in this game so far.