I've noticed something lately and I wonder if anyone else has noticed this; and if so, have they found a fix.
I like to film shows in manual focus as I think it gives me a little more control. Typically, I zoom all the way in on the main or center player, set the focus, and use that for much of the show.
I have noticed, however, when I zoom all the way out, the people on the stage will go out of focus. This is especially true if the stage isn't brightly lit. And I've also noticed that if there are people in front on me (between me and the stage) who are well lit, my camera seems to focus on them when it's zoomed out.