Recently 1.2 update came out for the 3DS version of Fire Emblem Warriors.
This patch brought a number of improvements with it, but also caused problems. Some players saw the framerate of the game was not as smooth and there where issues regarding the action buttons not correclty responding.
What obviously is a very undesirable thing, an update should improve things but in this case just made the experience worse in many cases instead.
Version 1.2.1 is out and this solves the problems mentioned once again.