Hello YG,
The error you are getting usually indicates that the step you are trying to re-direct to is not found. Since you say this occurs randomly, I presume that means it works sometimes? Is there only one step that causes causes error to occur? If it doesn't occur all of the time, is there some common action that occurs during the error sequences, say entering some flow control block, that doesn't occur when it runs normally? As juergen suggested, posting your code would be helpful, or if you were to elaborate on the two steps that are involved in this process (the calling step with the Post-Action code and the step being called) it would give us more information to use. With this information we should be able to better diagnose the problem.
John B.
Applications Engineer
National Instruments