多输入多输出分拣传送带出错

想做一个多输入多输出的分拣传送带的应用。分拣传动带第一个输入口进入的box从第一个输出出去，第二个输入口进入的box从第二个输出出去，分拣传送带每次只处理一个。

我现在是用开闭端口实现的，但是怎么会有一定的情况在box输出的时候报错。
有大佬遇到这种问题可以教一下萌新吗吗？感谢大佬们~

模型在附件；报错是这个：
time: 118.500000 exception: Exception Caught in FixedResource::getItemInfo(treenode flowitem)
time: 118.500000 exception: Exception Caught in FixedResource::setItemState(treenode flowitem, int state)
time: 118.500000 exception: Exception Caught in MergeSort::releaseItem(treenode item, int port) object: /MergeSort1
time: 118.500000 exception: Exception Caught in MergeSort::onTimerEvent(treenode involved, int code, char *datastr) object: /MergeSort1
time: 118.500000 exception: Exception Caught in ObjectFunction248__project_library_FlexSimObject_behaviour_eventfunctions_OnTimerEvent object: /MergeSort1 i: /MergeSort1>variables/sortedtable/4 class: /MergeSort1

time: 118.500000 exception: Exception caught in TreeNode::receivemessage()
time: 118.500000 exception: Exception caught in Executive::processeventinlist(). Throwing.
time: 118.500000 exception: Exception caught in Executive::steptotime(). Throwing.
time: 118.500000 exception: Exception caught in Executive::tick(). Throwing.
time: 118.500000 exception: int runthemessageloop() #4
exception: Executive::instance.tick();
time: 118.500000 exception: int runthemessageloop() #6

emm  我是flexsim  2019