Location (as well as date, time, light, air pressure...) is certainly a factor that should be used when classifying something though.
I think the problem is probably related to data collection / data integrity. At least in my case, I'm using an iPhone that has variously placed microphones and speakers. It isn't clear to me how to hold the tool to collect the sound. If it gets wet or grungy, it's not something that is user-serviceable. I don't have an easy way to tell if it even needs to be serviced. If you're relying on the microphone that follows you literally everywhere to remain clean & untarnished - maybe that's the problem?
My phone rides in my pocket, it picks up dust, it gets moist, it gets dropped, etc. Perhaps I'm projecting. Maybe your phone is untarnished and is working fine? Do you have data to back up the 100% fail rate across Europe and North America? It seems you might be projecting as well?