Apple TV not functioning properly

My Apple TV gives me an intermittent very low resolution picture when I run it. If I use the smart TV connection thru my wifi, (not using the Apple TV) my picture is perfect. Also, when I run apps for workouts for example, the Apple TV exhibits connection problem symptoms like buffering stutters, etc. If I run the apps thru my iPhone SE and screen mirror them to my TV the apps work great with no problems. Is the problem with the Apple TV unit, my wifi (Google Fiber, with a pod 10' away) or what? Thanks!