Hi Raid,
My Jupiter 3 is very sharp as well but the focus shifts towards the camera on the right half of a frame! (in the shot of the building, the left part of the image is sharp and contrasty and the right part is blurred as if focused at 5m! the tree in front of my window which is slightly blurred with all lenses is sharp on the right with the J3...
I did the shimming myself and find it very easy to do when using a groundglass and 21 or 28 as a loupe....in the center my focus with bessa or M3 is spot on and when shooting closeup and wide open I naturaly can´t notice the effect... I guess the front or rear element is slightly tilted....looks like I need to buy another one!
Fred