Can you see individual pixels that are not changing, or small areas?
Im guessing individual pixels, just sounded like it might have been more than just individual dots.
Generally, a dead pixel means it stays black, a stuck pixel will be constantly either red green or blue.
You say these areas are lighter than they should be, yet the problem does not show when the screen is displaying something thats black in those areas.
I don't know what to think, is it possible its a tiny chip in the plastic covering the screen rather than the LCD itself?
I guess you could try
a stuck pixel fixer, although their effectiveness always seem to be in debate.