Beautiful shower panel, have received loads of compliments. Installation went great. However, here we are just starting year 3 and it's all scalding water, all the time, bottom knob movement makes no difference. Really thankful I was in it when it started happening instead of one of our grandchildren. Help please? The little piece that sticks out of the bottom knob is also not attached. Hopefully this can be easily fixed without our entire tile wall being destroyed?