Instruct: Classify Amazon reviews into positive or negative sentiment
Query: mount doesn't stay put

I saw quite a few very positive reviews for this friction mount, and bought it for my new GPS C340. The mount works fine on highway driving, but with a dashboard that isn't perfectly flat and normal driving on curves and over bumps, the mount and GPS move all over the dashboard. I end up putting it between the seats so it doesn't go flying on a hard stop or rounding a curve. I have it in a Mazda 3...maybe it would work better in something with a flat dashboard, but I'm disappointed with it.