if you tap the side of the rifle would that make it reset? Is it like it’s just getting stuck a little? This happened to me on both my ar’s and I’ve heard about it from several people. There is often enough a burr or rough spot on the hammer hook that can cause a trigger to not reset properly. We discussed this in another thread.
https://palmettostatearmory.com/forum/t/trigger-not-resetting/9649