3.1 Lag

I'm working on a rather large orchestral score with a Windows 10 computer. Doing something as simple as lowering a note by a half-step takes maybe a full second., when it used to be near-instantaneous.
See the forum topic titled "Serious lag in 3.1, what?" I tend to agree with the author of this post (though I have not tested it with his score). The steps follow:

1) Open the score (do I need to put this...?)
2) Select any note (e.g., the harp in the first measure) and press the up/down arrow keys. Compare it with the response time of the left/right arrows.
3) You should hear the note sound before the note visually moves.
4) You can also try editing the title and subtitle text and you'll see that this takes longer than it should as well.

Sorry of I'm duplicating; I didn't want to scroll through the Tracker. Hope this can get fixed (soon).