Upload & Sell: On
Have you shown your test shots to Canon? Did you confirm that you are using a filter or no filter? If you are using a filter with the 50L, I would take the filter off.
I own this lens and while this lens is not the 24-70 II as far as sharpness is concerned, it does produce some rather sharp images even wide open which I have done many times.
I suggest that you return the lens to Canon and include your test shots. What "within range" means is that Canon won't recalibrate the lens if it is within a particular tolerence specific to the lens. Mine back focused slightly and I did have Canon re-calibrate the lens and they did confirm it was back-focusing. Once re-calibrated, it needs no AFMA.
Hope you can get things resolved as my 50L is one of my most used lenses.