I am having the same issue on my S8+, phone set to vibrate but intermittently making a sound on default Samsung sms app and WhatsApp. It's very frustrating as I can't take my phone into meetings. My friend has the same phone, the settings are The same and he doesn't have the same issue. I have tried a factory reset, and took the phone to a Samsung shop, they checked it over and couldn't see an issue, they did a reset via their computer but I still have the issue.
... View more