When a Bluetooth audio receiver disconnects, Windows reverts to another active audio connection.  However, the programs that were previously using the Bluetooth connection do not transfer to the new audio connection and reactivating the Bluetooth connection does not get the audio from those programs back.  

The only way to make them work again is to close the program and reopen it.  As a gamer - this is particularly a problem when batteries die.  Usually I would just swap the batteries in 10 seconds and turn the headphones back on, however it is not possible due to this issue.  Exiting the game would ruin my team's experience as 5+ minutes is approximately 10% of the game's average total time.