Shower For Low Ceilings My Shower Has Low Pressure When Set For Warm Temp,but Its Okay When Set For Cold Temp?

My shower has low pressure when set for warm temp,but its okay when set for cold temp? - shower for low ceilings

Hello everyone.my shower has low pressure when the temperature is hot, but good if anyone know what temp cold do.thanks in advance for the answers .. set
The shower is a Neptune Exotic 9.5kW Live at ukthanks