Hi all-

I'm having some trouble with the zombies' behaviour in my latest zombies map attempt. There are two semi-completed rooms in the map currently. The zombies in the first room work perfectly, but as soon as I enter the second room (titled 'sec2', and the debug prompt tells me 'all spawners in sec2 activated' when I open the door), the zombies from the three sec2 spawners don't enter the map. From two of the three spawners, the zombies spawn in and walk to the barriers, but then just stand there dumbstruck waving their heads around instead of breaking them and entering the playable zone. At the third spawner they don't even move, just stand where they are until they force despawn. 
Within Radiant I can see that the spawners are targeting the correct zones, yellow arrows and all, and they trigger correctly when I unlock sec2, I just can't get them to enter the barriers. Each of the three spawners has a bridge leading across a gap to their respective barricades, I wonder if that is somehow part of the problem. I should also note that at least one of the spawners worked correctly only when placed literally right against its respective barricade.
Screenshots - https://imgur.com/a/KWlMQpc

Any and all help is greatly appreciated. Thanks in advance