Since the camera was on my desk I started using it again. I put it back to what I thought was my normal mode and found it wouldn't release if I recomposed and the AF point wasn't in focus. Turns out I needed to put it back on Continuous when CSM 4 is turned on. Never noticed that before, but I rarely change settings once it's working well.
Originally Posted by tkamiya
I did a little digging on this odd behavior and it seems that it's a feature called Trap Focus (maybe not an intentional feature, but people treat it as such).
I tried a bunch of settings while messing around with the thing and couldn't reproduce the behavior you are seeing. What happens in Continuous mode; does the behavior change at all?