I've just returned from the Meadows near Atlanta, attending the "Turkey" shoot. We had max attendance with registration held to 550. Though misses can arrive at any random spot around the target, watching competitors at every tournament, I see 80% of misses falling behind. That's a huge number.
So I can concentrate on my own shooting, I've made a strict tournament rule for myself. No teaching. Sorry, but my shooting is important too. However, sometimes a simple reminder to someone on my squad can make a difference. This person is perpetually shooting behind crossers. No lectures from me, just a quiet suggestion to purposely increase the forward allowance by a considerable margin. Not always, but to the shooter's surprise, most of the time the targets break.
There are umpteen reasons for missing behind but the most common is because of our "don't miss" approach to the shot, resulting in aiming, measuring and muzzle deceleration.
To get in front and stay in front, learn to recognize these two feelings during the swing. Done incorrectly, the first is swinging with the parking brake on. It's tight and doesn't feel right—follow through is abbreviated—it seems like a parachute has opened beside the muzzle, slowing it down. The second is more a feeling of release. Swing and follow through speeds are increasing slightly, not decreasing. A released swing moves the odds in your favor of getting the X.
Here's one of my favorite quotes from a British author whose name escapes me at the moment. "You can be a boat oars length in front of a target and still hit it, but not one billionth of an inch behind it."