M32 command problem

Further to THIS TOPIC I can now add the following to the "end of job" gcode in Slic3r :-

M32 P !/MUSIC.GCO#

and it happily plays the music file :-)

If, however I put 2 or more in sequence Marlin throws an error "Exceeded subxxx call" and halts without playing anything.

According to the documentation the '#' flag is supposed to stop Marlin from going any further until the M32 has finished.

Have I got the wrong end of the stick or is the M32 command flawed ??

Regards,
Dave

#define SD_PROCEDURE_DEPTH 1 // Increase if you need more nested M32 calls

Yes, I checked that ... it is set to "1" ... but surely I only need ONE level because the M32 calls are not nested one within another ... just multiple M32 calls within the top level .GCO file ???
Dave