Diagnosis
This is usually a weak or unstable signal, not a broken screen. It happens when the wireless connection is struggling through walls or interference.
How to Fix It
First, rule out power issues. Make sure both the camera and monitor are plugged into outlets directly, not into power strips that might be sagging. Second, perform a re-pairing (Menu > Camera Pairing, then hold the button on the back of the camera). This often cleans up a noisy signal.
If That Didn't Work
The channel you're on is congested. On the monitor, go to Menu > Channel Select. Don't use Auto. Manually switch to Channel 1, then 2, then 3, then 4, leaving it on whichever one gives you a clean, stable picture.
Heads Up
Analog monitors like this one can show interference as visual snow, flicker, or lines. It's normal in tough environments. If the screen is perfect on battery right next to the camera but bad elsewhere, it's a range/interference issue, not a defect.