steps to reproduce: 

1. create an End Portal.
2. put a sunflower next to it,or look at the SUN.

observed results: 

1. sunflower facing the SUN movement(X-axis)
2. stars(End Portal Sky) movement(Z-axis)

expexted results: 

The stars in the Animated End Portal Sky should move in the X-axis like the SUN&clouds.