Things like this happen.
On 16-9.net there is a test of the zeiss 17-35. An almost perfect lens, but there is a ring arround the center of the image, that is soft. Yes: the center is sharp, the corners are sharp, but somewhere in the field it is a bit soft.
While I can understand this with a complicated lens like a wide-angle-zoom lens I don´t know why it happens with a simple thing like the 80/2,8.
Maybe it is just an adjustment error of your particular lens?
Been struggling with focus on the Mamiya 645ll and Leaf A75.
On the attached shot outside the studio, I auto focused on the abandoned crane in the center. F2.8. The camera seems to want to focus in front but the reason I'm posting is the center of the lens appears to be the softest. The 100% crops are 1. the center, 2. the ship on the left and way behind the crane, 3. the tour bus parking lot way in front and 4. the top of the crane.
Oh..no sharpening at all, through Raw Developer