Can you tell me more about your device (model, android version)? Does it crash around the same time each time? Is this during dialogue or during the overworld?
I'm going to look into optimizing the game, but sadly, I think that your device might not have enough RAM to run Under the Bridge consistently.
I'll include a Low-Graphics options in future mobile builds which *may* help your situation, though I can't be certain. Sorry for the inconvenience, but I'm hoping this feature will be what you need.