How to make pathfinders not collide

I'm trying to make a game with pathfinders similar to the zombies in Boxhead http://www.crazymonkeygames.com/Boxhead-2Play-Rooms.html

Here's the Capx: https://drive.google.com/open?id=1dxEzNaaI0Jxy4Gm35xrPyAk3T04gKjfL

So that they are always following you, and even follow to the closest spot when they can't get to you.

Even if that last part isn't possible, some problems I'm running into are:

#1 that I don't want the "enemy" sprites (the one with the pathfinder behavior) to overlap eachother, but when I give them the solid behavior or add eachother as obstacles they just run into eachother and then teleport all over the place so they aren't colliding.

#2 The enemies are not always finding very clear and apparent paths. for testing reasons I have it so that whenever I click it finds the path to the players location and moves along it, and sometimes I have to click repeatedly (click spam) for them to actually go through the path

#3, this one isn't quite a problem because I worked around it, but when I set the obstacles from solid to custom, and on the start of layout added the Solid sprite to the obstacle map, it wouldn't work, it would go right through.

#2 and #3 are resolved>> I added the obstacles to an Obstacles to the enemy On Enemy Created>

and changed the cell border to -1, and changed the size of the Enemy hitbox.

I still haven't found a solution for the first problem. ~~~~~~~~HOWEVER~~~~~~~~~~~ Now I have another problem//wondering. I want to make it so that if they can't find a path to the player, they can at least go to the closest point they can, Just like they do in boxhead. Because the players will be able to place obstacles.