Aim Down Sight frustration

[Jon K Lynn]

So finally got the game and I'm quite excited to play, but I have a terribly frustrating issue with ADS.  Whenever I pull trigger to use aim, it pops off one shot and then works normally as long as I hold the trigger.  It amounts to me basically giving every target a free warning shot.  It's probably something simple but I am just not seeing.  Playing on Win10 with Xbox One controller.  Any help  would be awesome!