After a mill is destroyed many times the explosion sound will repeat, even after the match and in the menu until you close the game and reopen it.
You can replicate this by watching a replay and once the opponents mill is destroyed the sound starts.

And on first launch most times I can't click anything and have to close task and restart game.

This happened to me too, with the sound of the mole hammering away trying to escape from the KSR prison.

This is also happening to me. I'm getting a looping unit switch sound every time I play. It's getting pretty annoying. None of my friends who bought it through Steam have this problem.