Diagnosis
The TV's wireless connection is likely weak or unstable. The internal antenna isn't great, especially if your router is far away or through walls.
How to Fix It
The fastest solution is to switch to a wired Ethernet connection. Plug a standard Ethernet cable from your router into the LAN port on the back of the TV. This immediately stabilizes the connection and often boosts speed for 4K streaming.
If That Didn't Work
You may need to clear the app cache. Go to All Settings > General > System > Storage > Internal Storage. Select 'Cached Data' and confirm clearing it. Then, go to Apps, select the problematic app (e.g., Netflix), and choose 'Clear Data'. You'll have to sign in again, but this often fixes corrupted app data.
Heads Up
Avoid using the TV's 'Quick Start+' (always-on) feature if you have connectivity issues. Go to All Settings > General > System > Additional Settings > Quick Start+ and turn it OFF. A full power cycle can resolve lingering network glitches.