Focus issues at 2.8 aperture with RIII and 24-70 GM

[whatcanido]

So I have been having this problem and wanted to see if anybody else is having the same issue. I don't really know if it's a problem with the camera or lens. 

When using eye AF at 2.8 most of my photos seem to turn out soft and not in focus when I'm not close to the subject. If I take say a headshot then it works most the time I think, but as soon as I move back and say include the whole body it looks soft. The green box seems to find the eye but pretty much every photo seems out of focus. If I stop down to f4 they all turn out super sharp. 

Been using continuous AF if this might have something to do with it. 

Had this combo for a year but take mostly landscapes so haven't used the 2.8 much. Initially thought it was just the fact that 2.8 wasn't as sharp as f4 and above but have testet it more and realize it's sharp when I hits and when I manual focus. 

Since most of the weight and price is the fact that it's 2.8 and not f4 it's annoying that I can't use it. 

 

[whatcanido]

So guess I'm the only one with this problem..

Have done some more testing now and this problem is just getting stranger and stranger. 

Previous I've only done the testing on my SO and a lot of here photos turn out a little soft from the look of it. Now I have testet it with two other people and they all pretty much turn out sharp as can be?!??!? Can someone explain this heh? Like can there be something weird with my SO's eyes that confuse the camera? She has normal eyes from what I can tell so I don't know. Was thinking maybe motion blur if she moves around more than others but I'm using up to 300-500 shutter speed  and it hasn't made a difference. 

¯\_(ツ)_/¯