I wouldn't consider myself an expert on autofocus, but use the Contax, Canons, Nikon, etc.
I have compared them briefly to the Hasselblad H1/2 and the older Mamiyas 1,2 and 3.
The difference between all the medium format is very small and more dependent on subject, lens, contrast than anything else.
The only exception might be the Pentax 645 which I used briefly in the film days and I thought had good autofocus.
For 35mm the Nikon wins hans down compared to the Canon, but does have a very small focus range in regards to the format so you can almost think of it as a single center focus more than a broad cover the frame focus point camera, though the Nikon's autofocus is amazingly accurate.
cowboy_filmThough given all of that I find the contax good. I've shot Ronaldhino kicking a ball at me at full speed in a dark studio and hit every frame, though I was working in a small area.
I've also shot a lot of very fast moving subject with little issue.
A lot of this depends on the contrast range and before I'd junk the system I'd rent a small light panel lcd, set the rheostat down low and to one side to add contrast and try that. I think you'll see a world of improvement. If that doesn't work I'd have the lenses looked at.
The two issues of the contax are slow sync speed, which usually isn't a problem for my work, but 1/90th to 1/60th is rather slow if their is a lot of ambient in the room, though once again not that big of an issue as I usually light for it or have learned how to mix light and not have a problem.
The real issue of the Contax is a non autofocus lens in the 100 to 120 mm range. That requires the macro which is manual focus.
I hit that most of the time, but sometimes autofocus at that mm would be nice and is one of the main reasons I consider the hasselblad because they have a very fast 2.2 autofocus 100 mm (or something) lens.
Try the lightpanel thing and see how it works for you, at least that's my thought.
IMO
BC
These are all tiny thumbnails so you can't tell, but it was all contax 645 and all focus down to the thread count.