walls zombies???

[Soldier . . .]

Zombies don't "see" walls, or any other object in the game for that matter.

They move based on a grid system.
For every zombie, the grid system looks for the closest hunter.
Then it send the zombie, through the quickest route over the grid, to the closest point on the grid near the hunter.
And from that grid point the zombie goes directly to the Hunter.
Whatever obstacle you see the zombie will go straight through.

So if a grid point on the other side of the wall is a bit closer to you that the one on the same side as you,
The zombie will be send to the point behind de wall and then directly towards you.

The people who placed the grid in the map know this and try there best to prevent this.
But it sometimes can happen that the placement of a point is just a little off.
Which is why these things happen.

This can be fixed yes but it takes time to find the right point(s).
But the most important thing here is that you need to give them the map name and the exact location where it happens.
Otherwise it will be (near) impossible to fix the problem.