Document Numbering.sequ

Hello,

I am trying to stamp and number multiple pdf files with the 'Document Numbering.sequ'. A very straight forward pdf action but it behaves strange. Randomly the 'Initial Value' of the numbering doesn't start but replies with 'NaN'. Secondly the imported 'Document Numbering' Action has to be re-imported randomly because it is missing in Adobe Acrobat. Who can help me with these issues?