Interesting, what would you say is the mechanism responsible for the crackling sound? You say there's no pressure, so there's nothing acting on the diaphragm, so unless you're mistaken, it's not flexing. Does that make sense?
Maybe try releasing the pressure again. The only way a foam tip wouldn't have any pressure is if there weren't any seal, wouldn't you agree?
Perhaps a short in the cable instead or something else.
Why don't we wait until we hear from Aurisonics, Matt has contacted Dale. Instead of you trying to troubleshoot the problem for me!