[jedalton]

95% of all buffering problems is do to slow Internet speed. Here's how Internet speed works if you subscribe to 600MB the only way you're gonna get that speed is if you hook your device directly to the router with a cable. if you stream it wirelessly then you only get 300MB and if you have other T v's cameras doorbell's tablet's phones hooked up to it it's gonna continue to reduce that speed. To check your Internet speed on your fire stick scroll over to the gear all the way on the right side of the home screen click on it scroll down to the network you'll see the network that you're connected to, Push the play button on your remote control then scroll to the right where it says run speed test click on the run speed test and wait for it to test speed. I subscribe to 1.2 Gbs speed but only have 395Mbs on my firestick due to all the other things I have connected to my internet. However. That is more than enough for my firestick.
Other options: unplug router and firestick for 2 minutes and then plug back in. If that doesn't help You may want to go back to cable.