Customer mixing issues with a shower cartridge in the master shower. Also experience large temperature fluctuations. Replaced the Moen shower cartridge and tested. The mixing is correct but there is scalding risks when other water is run. The Moen valve doesn’t appear to be pressure balancing to allow hot and cold water to be distributed evenly. But the water is also abnormally hotter than it should be. Temperature tested a tub and the water was over 150 degrees hot. Diagnosed this as a gas control valve malfunction. Ordered a new part under warranty so there’s no charge for the part, and discounted install by 50% due to a lot of work being done in the home recently. Made customer aware that shower valve replacement may be necessary for a proper repair even after temperature is corrected. Also may need to address prv due to large pressure drop on system.