You can also set a default value for the focus, so you do not have to do it every time you turn the unit on. Such a large change is unusual, for me for example it is always between 1585 and 1605. I also use AF a lot (it works well) and I verify that it works with a Bahtinov mask, which I 3D printed myself, as well as a dust cap.
By the way, ZWO, really, no dust cap? I know price is critical for this product but my 3D printer made me one for 5 cents.