My shower thermostat temperature control knob has become miscalibrated such that it is too cold (on the hottest setting its moderate temp). This happened once before, a plumber came and adjusted it such that the water temp was correct for the markings on the dial. Unfortunately I wasn't watching.
I know we have hot water, the other shower is fine, the hot water on the sink next to the shower in question is very hot. I have attached two pictures, one of the fixture (not even sure what brand it is) and another showing the inside. I could guess but guessing in plumbing usually doesn't end well. Help?