zombie survival server

[Apocalypse_Demon]

I have made my server a zombie survival one, but it keeps messing up, it keeps crashing my server for some reason, i don't know what the problem is.
my server is [RAGE] Zombie Survival, it just crashes randomly, but only when i do /zombiespawn r 10 60 5

[dzienny]

Well, probably zombiespawn command is bugged. Post the content of error log. It should point to the root of the problem.