Backlight issue after removal of lcd

Hi. I’m trying to expand my knowledge to separating glass and LCD. I have heating plate with suction and wire to separate the screen and lcd. I put the screen from the iPad Air 2 on 80 degrees C. Worked the wire and separated them. Checked the lcd and it was fine. But then I put it on the heater again and used glue tool (spinning stick thing) and then tried to clean with cloth and 99% alcohol. When almost cleaned I checked it again and this time it seemed like the backlight has broken. It’s sort of more dim on certain areas. Not so noticeable when colors are present, but on a white screen it’s terrible. Trying to post pic but doesn’t work. What in the process do I fail?