I have a similar problem. I have two that are runaway poopers, lol. They will go over to the middle of the pad and start pooping. They are so good about always going on the pad but before the poop lands they start running off the pad and therefor it misses.
If I am there standing in front of them though so they can't run they do good but for when I can't they end up running off.
But how can you blame a dog when it goes on the pad but is just to impatient for gravity to fully take effect?
I guess I should be thankful that they aren't runaway peers, lol.