Do you have any microphones connected to your system? Some headsets only support one audio source at a time, so if you have a headset with a built-in microphone, you can't use the built-in mic unless you switch to the "Phone Audio" source, which allows you to use both the audio and mic at the same time, but at the cost of reduced quality. Windows will automatically switch audio sources if it detects the microphone is being used.
I would suggest disabling all input devices under the Recording tab to see if it helps at all. I would also disable every speaker device except your primary speaker under the Playback tab.