5D Mark III and autofocus issues

Hello!

So I sold all my lenses along with my 7D, and now have the 5D MIII and Canon's 50mm 1.4 prime.
I'm noticing some strange stuff.

• The lens focuses beautifully on everything up close. I can use spot-AF and pinpoint a certain element on dollar note, will come up razor sharp, and if I use a large aperture, you can clearly see that the selected point is in the middle of the DoF.

• The lens has more trouble focusing on things that are little further away, like 2 or 3 meters. If I adjust the autofocus, I need to be on +15/+20 for the lens to focus correctly on objects that are not close.

• If I keep this +15/+20 adjustment, the camera will generally not focus correctly on close objects, but there are exceptions, 30% of the time focus will be good.

I'm a little puzzled. I would like to avoid calibration as I live in Cambodia, and I don't trust people here to handle the camera. Heard to many horror stories about the local shops.