For those still having issues with this, I would try taking camera and microphone permission away from all app.
Settings>Applications>Permission (Permission Manager) (you may have to open a menu to find this, the 3 dots upper right corner), then navigate to Camera and revoke permission for all apps there. Do the same for Microphone.
This is all just temporary and won't affect anything other than blocking apps from using these items in the background. When you use the app again or the next time it requires permission to use whichever feature it will simply ask again as if it were the first time. Here is where you have to be a detective though. Each time you grant permission to an app to use the camera or microphone you have to pay attention to if they stop working again. Once you've given permission to the app that was causing you trouble, you'll know because the issue will start again, you can then decide what to do about the app. Is it one that you can do without or do you just have to keep taking permission away from it and only allow it use whichever when you need that app?