I have a few user's accounts with this issue and after reviewing the log file with IFS today It was found that user ID creates a space in the user id when trying to process this request for s particular ID.      why this ID, why not others…..   have no Idea.   I have asked IFS to review and to enhance this function to remove non-visible space\char for this process.    I have had this random problem since 5.6  I am now at 6.4.   I hope this helps

Dennis