I have found with commands objects that they sometimes work when they are executed immediately after the solution, but when you try to run them a 2nd time without rerunning the solution they don't. Sometimes it's necessary to issue a resume command at the top of the commands object (which would require a database to be saved in Analysis Settings> Data Management>). In the APDL gui when you issue the SET command without resuming a database the program asks if you want to recreate the database from the nodes and elements on the rst file. Perhaps that doesn't work in batch mode.
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