Years ago I bought a 35mm Art to go with my 5Dc body. At the time I wasn't fully satisfied with the AF performance, so I bought the dock to microadjust the lens. It only needed a -3 adjustment at the furthest (editable) focusdistance and I've been really happy with the sharpness since then.
This winter I rented a 5D IV to shoot a wedding and I quickly adjusted the lens for that body. Although I used the camera's back screen for reviewing the settings and it was only a one day shoot the combo worked exactly like I felt it needed to.
This is where it gets interesting. Ever since I set the lens back to the settings which it worked perfectly with (I took a screenshot in the "before" situation to be sure) I haven't been satisfied like I was before. And I can't work out why it is.
Unfortunately I don't remember the adjustments I had for the rented body but I know they were significantly different from the ones with my own camera. I do recall upgrading the lens firmware, though.
Has anyone experienced something like this before or does anyone have a suggestion on how to solve this?