IMHO, bright spots tend to overwhelm the total picture as the system attempts to average out the brightness for the whole display.
A cheap experiment might be to make some 'eyebrows', keeping light from going up toward the camera.
Another thing you might try is cleaning the video cable connections (all of them) from the camera to the monitor.
MOTHER SHIP Winnebago View 24H (2007 Dodge Sprinter 3500 Chassis, 2008 Body)3.0 L M-B Diesel V6 bought used with 24K miles. Toad: ROCKY the Flying Squirrel.