Hi, my place is a little older and still has separate hot and cold handles in the shower and we like them that way. However the temperate mix doesn't work right. I either get all hot or all cold. I can adjust the handles all I like. Turn on hot and set cold at ANY level = hot. Turn on cold first and set hot at any level = cold. What can cause this and suggestions to fix? I understand that other systems can have mixing valves/pressure regulators etc but other than the handles all of the hardware is behind the wall.