Is Terrain Glitched????

So when I open up Unity the Terrain works. But it is not until I press play where everything messes up. Anything I click on the level or anything just paints grass. And when I go to grass to change it it doesn't change. I don't under stand the Problem. It only happens after I press the play button that all this happens. And in order for myself to fix it I have to restart my pc........ Is this a glitch if so how do I fix this????