• I always use AF-C with AF activation by the AF-On button. That way continuous focus is always on and I achieve focus lock by removing my thumb from the AF-On button.
• Priority is always set to Release. I'll decide when I want to trip the shutter. A slightly out-of-focus image is better than an in-focus image that you miss.
• Focus Tracking with Lock-On: I've experimented with this for years on many Nikon bodies. Now I just leave it "Off". Losing focus due to a subject block just doesn't happen to me all that often, and AF acquisition is getting better and better.
• Number of Focus Points: usually at 9 (body dependent). The other settings have occasional, limited, specific value and use.
I agree with Arthur. I wonder if you are targeting the middle of the uniform where there's no contract for the AF system to lock onto. And there is the possibility of blur. I'd crank up the shutter speed and let the ISO fly up as necessary and see if that improves results.
Jon Kandel A New York City Nikonian and Team Member Please visit my website and critique the images!