I removes the Pressure Balancing Valve in my Grohe model 19719 shower because I was getting no water. There was a small (1/2 inch by 1 1/2 inch) piece of very thin plastic stuck in the cold water inlet. I removed this and re-installed the Valve. Now I have water but akso a slow leak of about a drop a second that I cannot get rid of. No matter how I adjust the valve stem I cannot fine tune it enough to stop the drip. I did not take the valve apart but I did replace the O ring at both the cold and hot water inlets. Can anything be done other that replace the valve?