unity 5 wont let me switch between Raise/lower terrain and any of the other options

when ever i try to switch between any of the options to change the terrain of my game i use to plus the play button in order for the program to recognize the change, this include painting textures, or even changing brush size or brush type.

@RangerDog Well if I selected the bush size for example then I could move it from 25 to 100, but the program wouldn’t recognize the change unless I pushed play and then stopped the scene, and my brush would be at 100. It was like this for changing between brush size or painting high or any of the options to modify the hight of the terrain. I s solved the problem by going to Windows and settings and changing to default. Now I can change fluently between the different terrain options. Sorry for the bad wording beforehand.