Mobile security turning off ringer volume, wont allow adjustment

I keep finding my ringer volume off and cant adjust it up. I began shutting off running apps, when i shut off avast mobile security the volume immediately jumped back to full and i could adjust it again. I have missed many important calls due to this.

Hi, that is very strange, as there is nothing in AMS that turns the volume down. Is there a chance you mean Avast Battery Saver?

Set the phone to shake if a call comes in.
It is just a workaround, but should let you know when a call comes in so you can answer it.