Part of the problem may be the way you initially arrive at your own perfect temperature. Virtually all RV systems suffer from some version of this behavior. The solution from the Beaver site, many years ago, was as follows:
1) Turn on the water full hot
2) add cold - rotate the single lever control in newer AS - until your temperature preference is reached.
Use the Navy Shower Button
BTW some complain that the shower drips when the button is "on." This is by design to remind you the water isn't off and to help you remember to avoid Paula's problem (we all been there, Paula).