so normally you can toggle vibrate mode on/off by pressing the volume button once, when the volume slider appears in the top of the screen, pressing the bell on the left of the slider toggled between ring and vibrate.
normally when you toggle in and out of vibrate mode it will remember the ringer volume that is normally set. i.e. i normally have ringer at maximum, if i toggle on vibrate mode the slider goes all the way down, and if i toggle out of vibrate mode the slider goes right back up to maximum volume. I has been like this since kitkat i think?
problem is with the OP3 when i toggle out of vibrate mode the ringer is back on but only at a low level. Anyone have any idea why this happens?