Phew! I was really worried for a moment there :s.
You can just delete that wav file and the old one will be played. But alas - you now know the secret of loading custom hit sounds! This will be reimplemented in a better way in the future though, which is why it is totally undocumented.
Just to update you - I have been working on break sections and will probably have the code in place to run them tonight. I unfortunately have not had time to start on adding them in the editor. The syntax will be very straight forward, though so if all is working okay in tonight's release I will pass on an example of how to add these sections.
Keep up the bug reporting - I really want to get this game more stable asap
. The hits should still be audible at low volumes, so I'll classify this as a bug still.