Sorry for the bad experience, Andre. I've been through a half-dozen of them and the present one seems to work fine. The yield turned out to be pretty low, but I'm glad this one is still working as I find the peace of mind helpful when sleeping in my tent.
I did autopsies, bought replacement piezo speakers, etc. to try and revive the dead ones but when they're done, they're done.
All the best,
Dan. (...who just wants a *reliable* alarm)