Sometimes the TV input changes to the 4:3 aspect ratio after exiting the YouTube application.
Check the following:
- If the issue occurs, try turning the TV off then on again with the remote to recover.
- If there is a new TV software available, please download the new software and update the TV.
Follow these steps to perform the software update.
- Press the HOME button on the remote.
- Select Settings.
- Select Customer Support.
- Select Software Update.
- Select Network.