I have noticed this too. I think it may be clouds showing through the edges of the display.
I experimented a bit and saw that in clear skies it didn’t happen and in clouds there is a 1 pixel line around the displays. I think it was the caravan I first noticed it. When the plane is in motion, the pixel border shimmers against the straight edge of the displays.
I assume it is a similar issue to that of outlines around items in front of clouds since the last update.