What would make the crop coefficient different between two warm season grass zones? Everything ( type, soil, land, sun, etc) are all the same. Only difference is area of the two zones.
That should not have an effect, manually set it back and see if it happens again. I could not tell you why it got there, should not have, but if we can establish a pattern it is something with looking into on their side.
Alll warm season grass starts with a crop coefficient of 65%. When you select a new crop type, I would first tap the back button and it will save that crop type and adjust the advanced zone settings accordingly. If you go straight to Advanced zone settings they will not have been updated (until you tap the back button to save the new crop type).