I'm running the High Sierra (developer) beta build 17A315i on my late 2016 Macbook Pro with Radeon 455 GPU.
After a while, the discrete GPU's performance decreases significantly. The openCL score on Geekbench goes to 13k from 40k and FPS dips in all games. It seems that it is not using it's full potential since the fans do not really ramp up. Only a restart fixes the problem temporarily for a few hours before it goes back down even if I close all other applications. The intel GPU is unaffected.
Can anyone identify what I can try? No one has reported that it's the bug in the beta. What can I do to solve this issue? I've reset the NVRAM and SMC already, which didn't work.