PMFJI, but I just received my 90mm and I have the same kind of problem. The aperture ring doesn't seem to register fully, typically giving f/2.2 on the display with f/2 set on the ring. So if I turn it: 2.2 -> 2.2 again -> 2.5 -> 2.8, or conversely. At times it's an aperture between f/2.8 and f/4 that is displayed twice.
I can't say it happens every time I mount it, it even tends to occur less and less often. So... Electr(on)ical or hardware issue, or just poor contact? Do you think it justifies sending the lens back?
TIA for any advice. Best regards, Daniel