Found a diagram depicting my hotel shower's temperature dial.
@paco
My shower us the one on the left but the green band moves randomly while you're showering.
@paco Yβall need thermostatic valves.
My last place had two - one on the hot water tank, which mixed cold & hot water to a safe level, then another on the shower - once you set the temperature on one dial, the temperature stayed the same (once the hot water got there).