Here are some suggestions to help fix a flickering or flashing TV screen:

1. Check power and connections – Check that your power cables are connected securely. Make sure all of your HDMI ports are firmly connected to the wall. Power cycle your TV and unplug any other devices connected to it.
2. Check TV settings – Make sure the Picture size and format settings fit your TV. Changing the picture size may cause some apps to appear distorted.
3. Update your TV – Make sure your TV firmware is up to date. To check if there are software updates available, go to your TV settings and look for service updates or software updates.
4. Change your TV source – Try to changing your source by pressing the ‘Source’ button on your remote. You may want to cycle through the available sources until the flickering or flashing stops.