I've noticed, on my E-M1X and the AI Birds/Eye thing, that I get better results when I set the release to fire shutter immediately on pressing the shutter button instead of hunting continuously for the eye again for subsequent focus. Don't recall the menu setting, but it's something along the lines of fire and not lock the shutter unitl focus is achieved or something like that. I figure that since it first got the bird and then its eye, it already got its focus point locked on so it may as well fire then and not waste time looking for the eye again while I continue to press the shutter fully so it will release. By the time it hunts again and keeps me from firing the shutter, the bird has moved or gone. It's "Don't fire until focus is achieved" or somehting along that line in the menu which seems to result in the delay and out of focus eye shot.
Also, I have the 45mm f/1.2 Pro and I did notice that I had to tune the AF for all the 25 spots it allows for with that lens. Mine may have some field curvature or something as the outer AF tuning points seem to take more correction that the middle ones Often the eye AF one is nearer the outer tuning points for me. Testing and calibrating it was done wide open so a really narrow DOF, but stopping down seems to help a bit too. Came out with what is below as to tuning its AF.
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