Questions about sample 24_Urho2DSprite

Hey guys,
Today I tested the sample 24_Urho2DSprite, found that the sprites can’t move smoothly.
I reduced the sprite number to 20 to keep the fps 58~60, but the sprites still can’t move smoothly.
The sprites sometimes shake if you carefully watch.

I tested it on my iPhone6plus, the fps keeping 60 or 59.