the BasicConveyor problem

In my model I use some BasicConveyors,I run the model ,the system console sometimes print this message,simetimes not,I donot konw the reason ,why come out this problem.
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time: 27363.380798exception: Exception Caught in BasicConveyor::OnTimerEvent(fsnode *involved, int code, char *datastr) object: /crossroadD/crossroadD161/east3
time: 27363.380798exception: Exception Caught in ObjectFunction293__project_library_BasicConveyor_b ehaviour_eventfunctions_OnTimerEvent object: /crossroadD/crossroadD161/east3 i: /crossroadD/crossroadD161/east3/Product1105 class: /crossroadD/crossroadD161/east3
time: 27382.964798exception: Exception Caught in BasicConveyor::setitemconveystate(fsnode* item, double startpoint, double startspeed, double targetspeed, double accdec) object: /crossroadD/crossroadD161/east3
time: 27382.964798exception: Exception Caught in bcsetitemconveystate(fsnode* conveyor, fsnode* item, double startpoint, double startspeed, double destspeed, double accdec)
time: 27382.964798exception: Exception Caught in ObjectFunction045__project_exec_commandlist_bcseti temconveystate_node object: MAIN:/project/exec/commandlist/bcsetitemconveystate/node class: MAIN:/project/exec/commandlist/bcsetitemconveystate/node
time: 27523.686101exception: Exception Caught in BasicConveyor::setitemconveystate(fsnode* item, double startpoint, double startspeed, double targetspeed, double accdec) object: /crossroadD/crossroadD161/east3
time: 27523.686101exception: Exception Caught in bcsetitemconveystate(fsnode* conveyor, fsnode* item, double startpoint, double startspeed, double destspeed, double accdec)
time: 27523.686101exception: Exception Caught in ObjectFunction045__project_exec_commandlist_bcseti temconveystate_node object: MAIN:/project/exec/commandlist/bcsetitemconveystate/node class: MAIN:/project/exec/commandlist/bcsetitemconveystate/node
time: 27545.286101exception: Exception Caught in BasicConveyor::setitemconveystate(fsnode* item, double startpoint, double startspeed, double targetspeed, double accdec) object: /crossroadD/crossroadD161/east3
time: 27545.286101exception: Exception Caught in bcsetitemconveystate(fsnode* conveyor, fsnode* item, double startpoint, double startspeed, double destspeed, double accdec)
time: 27545.286101exception: Exception Caught in ObjectFunction045__project_exec_commandlist_bcseti temconveystate_node object: MAIN:/project/exec/commandlist/bcsetitemconveystate/node class: MAIN:/project/exec/commandlist/bcsetitemconveystate/node"

Usually this means that you are having a pointer to an object that doesn't exists. In your case on object "east3" when creating the code for the basic conveyor probably sometimes your item pointer is not correct (either involved or item) It could also be the conveyor pointer but that seems unlikely.

So you could put a check (objectexists) in front of the code that is causing the problem and check when it doesn't exist and why.

hi thank you , May not be the reason.because i write code in onentry trigger and oncover trigger , the item is parnode(1);

Ok then this message might appear some in the chain of events. So your onentry or oncover might trigger something and that is cause of your problem but at this trigger the error is thrown.

If your error is reproducable by switching the repeat random streams on, you can open the list with events and step through the events looking which event is causing this problem and check inside that event.