Order of elements reflects execution of a workflow with a CMD tool

When you create a workflow that contains an element with a command line tool, the order of the elements in the UWL file affects the result. The workflow is the following:

Read File List > Element with CMD > Write Plain Text

Element with CMD has ports:
1)  "in" of type "String" (read as "String value")
2) "out" of type "String" (write as "Text file")

If you add the element with CMD after the write plain text element, an internal error occurs in the Workflow Designer:

No workers are ready, while not all workers are done. Workflow is broken?