Whatever problem you might have with the sound, if now appears to be fixed, it surely wasn't GSX since we haven't changed anything in the sound.
However, what the GSX sound engine can't do, is to dynamically switch to a different audio device after it started which means, if you switch in/out from VR and this results in the audio device switching in Windows, GSX won't detect the change, you will still have to enter the GSX Sound settings, change it to the correct device and restart GSX.
Note that, during the loading time from the MSFS Main Menu to the start of the flight, GSX will always restart automatically so, if you switched in/out of VR on the Main Menu, that might be a good time to check the GSX audio device as well, since entering a flight would restart it in any case.