Signal quality

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I have Sling TV for some channels I don't get on the Welcome Pack with Dish. I watch NBA on TNT and lately the signal drops and the picture quality gets grainy and fuzzy and then comes back to HD quality. It isn't constant but happens off and on with TNT and other channels. Our internet wifi is fine because other streaming services like Watch ABC, Amazon, and Hulu work just fine. Sling tried to help by having me do the usual reset the roku, reload the app and nothing helped.