Shower temp adjustment gets too hot

when you push the button on the shower head, the water will flow back through the hot line or cold line at the valves. The way if flows depends on which side has slightly higher pressure and this is randome. Install a sharkbite check valve on the cold and hot supply lines and you will never have this problem again.
In my cabin (has complete rv water system) we would always get a blast of very hot after having the button off for a minute. Last week I installed two sharkbit check valves and it now comes back on the same temp as when shut off.