I have only had my Samsung Galaxy S5 for two weeks but it has an annoying problem. Every few days, the ringer volume will suddenly drop to nothing and I can only tell this when I feel/hear the phone vibrating. Going in to Settings -> Sounds shows that all of the sound sliders are stuck on mute and won't budge when I try to increase them. Accessibility -> All Sounds Off is not clicked, already checked that. The volume keys on the side of the phone are not blocked or being depressed, checked that. The only solution that works is to reboot the phone, and that is stupid and not a "fix". It is only a temporary kludge until the problem happens again a few days later.
This may be the first time I ever return a phone for a refund. Not very impressed with this S5.
This is an unusual problem with the Galaxy S5, and I can understand your concerns. I would suggest running the phone in Safe Mode http://vz.to/1hhYjUF for a few days to see if the issue is related to a third party app you may have downloaded.
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