Trapping rats fails

I've tried to use the spike traps to kill sewer rats but they run over them without being affected. If I run over them i take half my hit points... is this supposed to happen?

 

Those traps are supposed to damage anyone who steps on them, be it the player, a friend or a foe.

 

That's what I thought but having a rat standing on a trap while attacking you for several turns seems to indicate otherwise. I tried finding the script for the mechanical trap but it doesn't have anything inside it, just a wall of blue.

Curiously boars or wolves going over a trap set it off.

 

A glitch can cause someone to step on a trap without activating it. Happened a few times for me with my player character, not sure if it can happen for NPCs as well.

Did this happen just once or is it a recurring problem? Also, which rats exactly did you try the trap on?

 

It's recurring. It seems to happen on sewer rats and my custom rats. Haven't tried on other pre existing rats.