20 Most Recent Moen Posi-Temp Single HandleTub And Shower Faucet - Page 9 Questions & Answers

You can try lubrication, usually silicone based. Some designs certainly do bind up faster than others. I prefer American Standard for just this reason. Hard to throw away a lifetime warranty faucet, but if you have to service it all of the time, eventually you need a new one.

return it for an exchange

thermostat or eliment in small tank on the shower unit

it sounds like the tub filler itself. When you pull the knob up it's supposed to divert the water to the shower, if it's coming out both, I'd look at that piece, inexpensive and easy to replace

sounds like either the cold water that feeds the other half got shut off, or the mixer in the valve for controlling the water temperature is broken....most likely the water got shut off. better go to the water source and trace the cold water feed pipe ,looking for a shut off valve....it could also be behind the shower panel, then turn or rotate the valve the other way and go test the water to see if you can adjust the temperature now.....if not, then replace your hardware.......in the mean time, you could turn the temperature down on the water heater so that you won't scald yourself in the shower til you have time to fix it properly.