When a player is flying an airplane in medium overcast value, player gives the airplane a Roll Right or Left and some clouds disappear
You can get this bug by flying an airplane or by flying the SPLENDID CAMERA, giving it a roll(bank) of 57-60°

Look at the two screenshots below, same position, on the first one the camera 53° bank and cloud is visible, on the second one 57° bank and cloud is gone

Watch the two YT videos: on the airplane and SPLENDID CAMERA