Bought a little cabin the previous owner built himself and been fixing stuff he didn't get right. I noticed when my wife showered a drip coming from under the shower. Investigated thinking he didn't get the pex crimped but its actually leaking from the mixing valve. It only leaks when the water is on. I tool it apart thinking I could try and tighten on the cartridge some like I have on previous mixing valve to see if it would seat it better and stop the leak but I can't figure out what to tighten where. Searched but can only find people with leaking faucets not the actual mixing valve itself. The water it spraying out from under the chrome cover over the cartridge back into the wall. I didn't wanna start jacking with it and mess it up worse. Any help is appreciated.