The mainspring screw under the grip should always be completely tight. Many folks will loosen or even file down the screw in order to get a lighter trigger pull and what they will usually get will be light strikes.
Tightening down the screw will most likely fix the problem for you. The rounds firing in SA when they would not fire in DA also confirms this pretty well.
Lots of times on a revolver that has had the trigger and innards reworked by a professional will suffer from light strikes also. I have had such revolvers that will only reliably fire in DA with Federal primers which are the easiest to light off. It is a trade off for fast DA shooting in competition.
Good Luck and give us an update of your next range trip.