Hey Troy, Oscar,
I found that article about Vibrandoneon care.
It says that you should only play with the original mouthpiece to prevent the air chamber from moisture. As soon as you hear a gurgling noise you should blow out the mouthpiece (meaning every five to ten minutes!). After use you should position the Vibrandoneon upright with open moisture holes – for this I use a K&M guitar stand like this one:
You should never keep it in the case but always keep it mounted when you don’t play. The case is ONLY for transport!
Well, that’s what they say here; I really don’t know if this could guarantee a longer life of the Vibrandoneon, but perhaps it’s worth a try… Or do you take all these precautions and it still doesn’t work properly?