If send PC to sleep when its playback video(mp4) in browsers, after wake up, idle clock stuck on UVD State 450/1200 mhz, clock may go higher up to 860/1200 mhz but dont back to stock idle state 300/150 mhz. Only reboot PC fix this problem. Videocard in stock mode, not overclocked. Sorry for my bad english.
My card: PowerColor HD7850 (AX7850 2GBD5-2DH)
Driver: 18.3.4 (problem was on all version driver)
OS: Windows 10 Pro 1709 (problem was on 7,8,8.1)
I've reported that particular effect and the whole CGN 1.0 bug too many times, AMD knows about it but still hasn't provided a solution. If you use 16.7.2, those were the last drivers without the bug on the affected cards.
If you don't wish to restart your computer, just download CRU (Custom resolution utility) and run restart64.exe. It'll restart your graphics driver, and normal clocks will be back.