It occurred to me that if you have multiple installs of V4/M4 across different runtime folders linked to the same Library, the .bat file command may not work.  In your case, this is not an isolated problem, it's rare but not uncommon.  The old EXP system developed for V4 and M4 installers did present its challenges when they were released but it was under a different environmental condition with EXE files.  I thought they eliminated this issue by going with the zip format.