support.microsoft[.]com/en-us/help/4489899/windows-10-update-kb4489899
Update Tuesday, & if you're running win10 v. 1809 [the fall 2018 update version], today's hotfix fixes the problem of reduced gaming performance, but introduces a new problem, *Only If* your PC has more than one audio device, e.g. on-board sound + a sound card.
After installing this update on machines that have multiple audio devices, applications that provide advanced options for internal or external audio output devices may stop working unexpectedly. This issue occurs for users that select an audio output device different from the “Default Audio Device”. Examples of applications that may stop working include:Windows Media Player
Realtek HD Audio Manager
Sound Blaster Control Panel
* * *Microsoft is working on a resolution and estimates a solution will be available in late March 2019.