@Yiğit S
When I opened your model the Process Flow appears to not be functioning at the moment. I am using version 20.0.5 to test it and the problem may be due to a difference between our versions.
However, I noticed that both Queue1 and Rack1 are setup to use TaskExecuter1 as a transporter in their flow tabs. After disabling the process flow the model appears to run without any errors. The reason that TaskExecuter1 is moving items from the rack to Queue2 is because the flow tab on Rack1 is setup to use TaskExecuter1 to move the items to Queu2 (see picture).

If you don't want TaskExecuter1 to move items out of the rack you could uncheck the Use Transport box or connect a different task executer to Rack1.
If you could clarify what you are trying to do in your model a little more I think we may be able to help you find a good solution.
Brandon
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Brandon Peterson
Principal Technology Consultant
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