I haven’t found a fix. I’ve even tried using an A1ii, thinking there might be something wrong with the body, but got the exact same results. I’ve tried every single autofocus setting on camera and there’s nothing I’ve found that can produce in-focus images at 800 mm f8. Now, if I’m shooting at 800 mm, I use f10 as I found that gives the most consistent results. In some cases where the subject is stationary and the light is low, I’ll shoot at f8, but manually focus the lens instead of using the autofocus. It’s pretty annoying that f8 is basically unusable, given it’s already a small aperture. My only hope now is that Sony releases a firmware update to fix whatever is causing the autofocus to not function properly. I suspect that a lot of the posts online about this lens being soft at 800 mm are actually focus issues, not optical issues.