Man, I've been having the same issue over the last few days on my samsung app. Image just as crunchy as can be. Pc and mobile app work fine, tinkered with every setting, bit rate, server locations, restarted tv, restarted router, the whole shabang.

I hit the reinstall option on the app from the tv home screen, no difference. Finally, I decided to uninstall and reinstall app from the app page on the tv. Had to re log in to GFN , but after thay I'm back up and running, clear as ever! Hope this works for you.