It’s normal behavior & I believe it’s because it’s not a true servo lens. Many if not all cameras in this category do this. I don’t like it, but it is what it is.
James, you say yours doesn’t do this… but I think you’re not understanding. Put your A1 in TV (locked) or manual mode. Start out wide, then zoom in. Your iris WILL close down a bit… such as around f2.6 or whatever it is. Zoom back out to wide & it opens up to the original value.
Bill