Your case is just likely that rare where the evidence can point to such a specific conclusion. The Zombie AI does not target specifically any type of infrastructure, other than just generally player made objects. They will play through a space or an object simply because its there and in the way. From what I have observed the zombie pathing logic is a bit less rigidly defined than it has been in the past, and that change has been made in the time you've been away. I think the reason for this was to make them seem a bit more chaotic and less a thinking foe.
But, for the reasons above I think it's just a mere coincidence, as I've not heard of this being an issue for a really long time.