How the hell does he keep getting out?

My little gelding is about 14.1hh , he's is enclosed in a field with no trees, but he has a little shelter in the middle of the field, the ground is pretty much flat, the fencing has 2, 2" x 6" planks, one about a foot and a half off the ground and another about 5 feet off the ground with electric tape running through the middle of the two, I know for sure the fence is working I shocked myself the other day, -_- anyways every morning i come to check on him and he is about 30 from the fence on the OTHER side of the fence. I know ge can't jump that high he's to clumsy. How can he possibily get our?! The gate is always securly fastened, and he isnt kept with other horses but he never has been and he really shows no intrest:/