is it just me or do zombies have a habit of shuffling around on the barricade entry brick without actively attacking me
that and when i'm around on a certain chunk of node bricks the server lags to hell
(Even though I have answered your question when you have joined my server yesterday, just gonna reply anyway.)
For the server that lags to hell, that sounds like an impossible path scenario occurring, thus it ends up trying to search every single node in the map; be sure to re-check your node connections once more and see if you might have missed anything.
For the barricade entry bricks, it may be they are placed too far away from the barricade, or something else.