But you say it used to go completely to zero and now it doesn’t. That makes me suspect that something else is up because I’ve never seen one go to dead quiet with the volume on zero unless your amp is not very powerful in the first place.
The only way I would be able to confirm if the difference is now really significant is to examine the unit. If it’s enough of a problem that you think it warrants sending it here, you’re welcome to do that.