I found a bug that makes all the zombies go idle if you stand in the right place on Gasoline. On the left side of the store near the car, some of the sidewalk, covered with the shadow, a small portion of it has assumingly no path-finding for the zombies, which would make them just stop moving until you’re no longer in the area. It is a pretty small spot, but I came across it by accident. I included the screenshots below (Apologies that they’re sort of compressed, as I don’t have uncompressed copies).
I tagged this bug as “Ghost Mode” because of what it does, and that I didn’t have a much better name for this.