Shower has a Grohe thermostatic reverse cartridge either a 4703200 3/4 or 47040000 1/2 not sure which but have had a qualified honorable plumber out who has replace the cartridge 4 times. First time the carttidge cost was approx $300(see it on the net for $195 to $264) and in short order it stuck and plumber replaced it labor only and said Grohe gave him new one saying problems with these and kits to fix them for all but the reverse model. So 4 valves and all get stuck after 2 months or so. He replaces them labor only but this is getting expensive! Water pressure same as it has been for 9 years?? Plumber and 2nd opinion say clueless what to do but cut out wall and replace with a Moen valve. I say ok but wife won't go for ruining her wall paper. Ideas?