I just talked to our plumber, after phone stalking him for days. He told me that he can’t find the right valve and we might need a whole new shower. Yeah, my BS alarm went off too. Especially since I was able to Google search “3 knob shower valve” and Amazon gave me a picture of something that looks just like what’s currently installed.
I need to stop telling the repair people that I’m a new homeowner. They keep mistaking that to mean naive.