Aaaaahhhhhh ...
I got it working ... it was just my stupid mistake.
while(media_playing(mHandle) > 0)
is totally wrong ... it must be
while(media_playing(mHandle) != 0)
what a stupid mistake ...
In all cases where I got the strange behaviour, media_playing returned a value < 0 ... that's all .... grrrrrr ....
Sorry for wasting your time.
Regards,
Pegamode.