What happened to the Duracell batteries?! joking aside, the Energizers have a far more contrasty color scheme, so you can’t rule out that being the reason the lens could focus better.
Glad you’re happier with it, but chances are the first one was probably fine, too. This is why I no longer really test lenses much… it can throw up all sorts of real or imagined issues. As long as the photos look ok amd the edges more or less similar then I’m happy.