I know the display is interlaced, but this happens on top of it. So not only it flickers, but it also moves strangely, sort of like "burning" effect.
I have tried it in WinUAE which has a "flicker fixer" and got exactly the same problem. In fact the screen looks even worse on WinUAE.
Just checked Youtube video and it looks totally ok there, and exactly as i remember when playing it on Amiga back in 94.