Sorry to revive a dead post but looks like I've got a similar issue:
Noticed a large one a little while back and then just more recently saw a couple others (could have been there all along just not really noticed till now) They only appear on lighter backgrounds usually, but mostly seen on white and light blues.
Close up of the biggest one, looks like the pixels are working fine:
Since nobody answered I'm guessing there is no solution to this, but I am curious if timil notice it getting worse or anything since you last posted.
Thanks!