The easiest way to debug the error is to use a (temporary) CMD file.
Call a TempBatchFile.cmd with the path and then have a look what exactly do you get in this batch file by ECHO %1 from inside the batch file to see what you get passed from Mp3tag.
It could be that the call of mp3advanced.py from Mp3tag does not use the underlying python environment. In a batch file you could easy start it with
C:\PathToPython\python.exe D:\rips\_IN\mp3advanced.py %1
And you could try to use the current parameter without double quotes, just
$cutRight(%_folderpath%,1)