I've had quite a few clients with the exact same problem. So what I have them do is RAISE THE LITTER BOX. Put it on a square frame that raises it off the ground so that your dog-regardless of sex- has to make an effort to actually GET IN the litterbox to go potty. Many of the problems w/ litterbox training-especially males-is simply due to them either A: being lazy or B: they begin to hike their leg. Problem is that their front legs are in the box and the rear legs are out the box...and so on.
So, try raising the litter box as mentioned above and see if that aleviates your problem(s). Just remember that it should be a frame that it rests on and not feet. So that the litter box still remains level and steady when he's in it. And you'll need to eye ball just how high it needs to be raised. More or less just high enough so that he can't just walk in it, he'll need to make a little effort to jump slightly to get in. There you go!
Keep us posted!
