last frame not clean up

i upgraded from 4.6.6 to 5.1 , when my android device open the game, the last frame alwasy not clean up, eg : when i opened the game and the scene has loaded , last screen (unity landing)is not clean up , some black line block the view (any other device has similar problem, some has black "noise" pattern on the view) , i have tried to update the NGUI(3.7.x to 3.9) but still the same , so it may not be the ngui version problem.