Maybe it depends on how they're made. My Galaxy S5's cover never had any issues, even after a few months with a bulging battery. It stayed in place no problem,

Maybe it depends on how they're made. My Galaxy S5's cover never had any issues, even after a few months with a bulging battery. It stayed in place no problem, and the phone was still waterproof enough to not care at all about being in the pouring rain on a motorcycle for several hours at a time.