I am on my third copy of the 50 L and as much I love parts of this lens I have SERIOUS AF problems....
If I aim at 30 meters the lens is dead on with midpoints and 10 meters in front on the outer points. I adjust to make the outer work, and then it's waaay behind when I use midpoints.
It was the same with the two others, this one is production code UA03, so it's brand new. It's much better than the two others for stabillity, the two others were all over and damn near impossible to MA, never got them to be consistent at one setting.
But it still is the same issue. try the second to last row to the right/left, which are crosstypes (5d3) and it misses both in Ai and One Shot, with spot, single, expanded by four or 9, I can try 40 times, and just doesn't hit. use points closer to the middle and it's sharper than any of the two others, by far.
Anyone else experiencing this ? As I said, three copies used on three different bodies, 1d4, 5d2 and 5d3.
And for the record, neither copies of my 85 L II and 35 had or have this issue.