I reset the cam (and reconfigured it) and also cleaned the contacts on both the body and the lens.
I mentioned earlier it's hard to reproduce the issue. I also mentioned it's as if sometimes the AF won't comply at all.
I did some shots last night, where I took some photos of the monitor screen - though they weren't all tack sharp, they were good enough and better than the kind of issue I'm experiencing. If I had shown those to here, someone might have said: I don't see any real problem.
I just tried again now and the results are (drumroll) suddenly completely different. The other body behaved better, but it does fluctuate quiet a bit as well. I repeated the test using this forum as target, which was the case yesterday as well, to see if the forum colors might have an effect but the results were still very bad.
I must admit one thing: Last year I had some really bad experiences with sending in a camera for repairs (multiple reasons), and I now have trust issues with service centers. And since the body seemingly behaves randomly, I fear they will dismiss there is a problem instead of testing thoroughly, costing me both money and additional time for sending it back in again. Are there any kind of tests you guys can suggest, that should nail the fact, that I do have a problem?
Btw. You can see the 16 shots from today here: First 8 are from the problematic body, while the remainder 8 are from my other body. both using same lens, Sigma 17-50mm @ f2.8 1/100 (or so).
2014.06.05 - zafariqbal