Ah yes, you are now discovering something that many of us target shooter and veteran shooters have known for quite a while not to mention something we've been preaching on here for some time. When shooting a release, regardless of triggering style, thumb, index finger, pinky or "Stans" type release, you should do so using back tension, There are too many sensory nerves in the tips of your index finger to rely when triggering a release. (Between mind and finger) When triggering an index trigger release you should shorten the release so your finger falls over the release so it fits into your second knuckle and apply back tension. What you did was change your triggering style and it's a matter of time until you develope the same bad habits as pulling the trigger with your index finger. Wait and see, otherwise, shorten your release, lay your finger over and apply back tension.

It's tougher in a hunting situation however, it'll make you a better target shooter.