I think mine 23 ACD may be damage because the foam was crush, but I read on Apple Forum and a fews user who own the ACD have this problem too. When you push your screen in gently at the top left or right corner inward repeatedly, does it move inward a couple of centimeter? I can see it move in forward and follow by a clicking sound. Like it kinda loose. You may want to try all four corner too. I'm thinking how the ACD are built that no screw hold it together some are a little bit loose? Mine is kinda loose so the backlight bleed is very severe. Maybe this is the reason for the backlight bleed depend on how tight it was put together? I would consider this a defect. Does other people ACD screen experiment this?