Oh, UnitAlive. But I don't think the script has any problem, anyway, have you tried to update jasshelper?
scope Spell private struct Data endstruct private function Periodic takes nothing returns boolean local Data d = KT_GetData() //If you want to stop, return true //Else, return false endfunction private function Act takes nothing returns nothing local Data d = Data.create() //Do stuffs. call KT_Add(function Periodic, d, 15.) endfunction endscope