This doesn't really make sense since all this does is forward the hook to plugins. The actual hooking is handled by sourcehook. The only way this doesn't work is if the hook isn't being fired by sourcehook or the callback isn't called, but i don't see how that is possible. Does it start to work after again? like one map it doesn't next it works again? Also i need code to see/test. How many map changes till it stops working?
Edit:
I actually finally remembered what the issue was before and fixed the issue when someone else reported it. What version are you running?