Why does my s5 keep switching off vibrate mode?

[AC Question]

Samsung S5, marshmallow 6.0.1. Whenever I turn the phone on vibrate it randomly switches back to sound minutes later. I tried a hard restart.

 

[belodion]

Try Safe Mode.

 

[Nathan Meyers]

Having the same issue. Has anybody found a solution yet? I've seen multiple people reporting this problem.