Diagnosis
The TV's wireless chip can struggle with certain router signals, especially congested 2.4GHz networks or those using specific security protocols.
How to Fix It
Forget the network and reconnect with a manual IP. Go to Settings > Network & Internet > Your network > 'Forget'. Reconnect, but when prompted, select 'Advanced' and manually set an IP address outside your router's DHCP range (e.g., if your router gives out .100-.200, use .50). Also, set DNS to 8.8.8.8 and 8.8.4.4 (Google).
If That Didn't Work
Switch your router's Wi-Fi band. If you have a dual-band router, create a separate network name (SSID) for the 5GHz band and connect the TV to that. The 5GHz band is typically less congested and faster, though its range is shorter.
Heads Up
For absolute stability, use a wired Ethernet connection. The KD50X80L has a 10/100 Ethernet port. If distance is an issue, a powerline Ethernet adapter is more reliable than Wi-Fi for streaming.