The 3pm's are rarely in UHD 60fps as they are foreign sources. At least we can get english commentary now.
Even so, HD streams should be blur/judder free. Switch around to get the best stream, then check below.
There are two settings you need to look out for. One on the Firestick, one in your App. Look for Picture settings.
On the Firestick, is called "Frame rate matching". It only works if your app supports it. Switch it ON.
On your app, it will be called something like "Frame rate SWITCHING". If the stream is passing on the original source material, the Stick and app will work it all out. You can normally tell if your TV is frame matching as it will go blank for a second when you switch sources.
Most people think picture judder is source related (which it can be). But most of the time it is your setup causing the issues.