Well, thanks for the input and at least I know I'm not crazy. Or if I am, it's a group psychosis.
My only disappointment was that while placing the bunker showed good quality sight lines, when the shooting started, the MG crew sat on its huge pile of ammo and smoked while enemy troops were pouring through the hillside it was supposed to be covering.
I guess I'll have to experiment with the editor to see if I can get a feel for the terrain configuration that causes this.