Observing dark tint towards top/bottom edges - more conspicuous in mobile app in landscape mode

Not sure if anyone has observed it. We are observing that the video has dark tint towards top/down edges. It is noticeable in mobile app and more conspicuous in app landscape mode. We observed it while trying to capture a white board.

Since I have not found any reports of it in Jitsi forum, I am hesitant to ask questions. My question would be how to eliminate it.