AI::Controller exception

[number3]

I've been playing around with activating and deactivating units. After activating a unit I assign it a task and then deactivate it after 5 minutes. But usually by the 1st or 2nd deactivate occurs I get an error message and DCS crashes

 

00095.320 ALERT   WORLDGENERAL: AI::Controller exception: No state creator for task "AttackGroup" and controller "wcColumn"

 

Here is is basically what I have and where I've been able to isolate where the problem might be. However I'm not sure what the problem is exactly. Anyone come across this error before and know what might be the cause? :helpsmilie:

 

function activate_untis(...)
   ...
   local defender_group = Group.getByName(defender_group_table[zone_index])
    trigger.action.activateGroup(defender_group)


   local attacker_group = Group.getByName(attack_group_table[zone_index])
   trigger.action.activateGroup(attacker_group)


   -- Set infantry to be immortal
   local controller = attacker_group:getController()

   set_immortal = { 
       id = 'SetImmortal', 
       params = { 
           value = true 
       }
   }
   Controller.setCommand(controller, set_immortal) 
   
   -- Set target of attacking group
   if (nil ~= defender_group or nil ~= defender_group.id) then

       attack_group_task = {
           id = 'AttackGroup',
           params = {
               groupId = defender_group.id
           }
       }
       Controller.pushTask(controller, attack_group_task) 
   end
.....

   scheduleaaaspotting = mist.scheduleFunction(deactivate_group, {attacker_group}, timer.getTime() + 300, 300)

end

function deactivate_group(group_obj)
   mist.removeFunction(scheduleaaaspotting );
   if (nil ~= group_obj) then
       local controller = group_obj:getController()

       Controller.resetTask(controller)
       trigger.action.deactivateGroup(group_obj)
   end
end