Hi - fairly new to Sony and today when out taking butterfly photos a few times the camera (with the Sony 100-400 lens) refused to focus. I use aperture priority, AF-C and medium rate. Use also the AF On button and have taken focus off the shutter button. It would focus in wide, zone, but none of the other focus modes. I wasn't too close to the subject but that wasn't the problem anyway as it wouldn't focus on anything unless it was in wide or zone. Will have to trawl through the settings and the manual as it was probably something I had done as I have found so far Sony kit is quite reliable.