Regarding the "Failed to start audio capture" error message, Windows allows programs to use only one audio device at one time.
If the audio device is used by another program, you will see the "Failed to start audio capture" error message.
Please refer to the second solution again on the linked FAQ page.
Bandicam error message: Failed to start audio capture
https://www.bandicam.com/faqs/failed-to ... o-capture/
If you still have the same issue after that, please let us know if you are able to record the game with the "Record Sound" option unchecked.