I’m humbled at this moment. I have built a shower myself using great advice from this forum. Now have a new house that I can’t figure out the hot cold valve. It is locked in position. I looked around and cannot find any Allen set screw holding it in. All I have is this one “button” on the side. Thoughts on how to turn this? Wife says shower not hot enough. Hot tankless showing 150-160 on output when she is showering but shower is Lukewarm at best.