Change files to waveplayer

I’ve got trouble using waveplayer node with 7.1 soundcard to play a wavefile each channel/box.
There is a strange behaviour if I change my soundfile name, switching between german and english sounds. At changing inputfiles it looses some boxes randomly. Sometimes I got 6, sometimes 4 boxes left only.
Not changing filenames, it works fine and reliable - actually after V4-init. Error occurs only if I change filenames.

Im using beta20, mono-wave at 44.1 khz and a 7.1 soundcard. Tried different drivers at AudioOut too.
Any idea or workaround (besides the videostream-trick to build one big file and then to seek).