Discovered when I was updating the Blinking Stars mod to 1.21. I noticed a flaw in the way stars are rendered in Vanilla. The new code didn't accout for Mutable Vectors, resulting the star to be half the size and shifted to the corner. I did confirm this is also in Vanilla minecraft with no modloader installed.

How to reproduce

1. Load 2 instances of minecraft (1.20.4 and 1.21) and put them side to side
2. Load a new world on both instances with commands enabled.
3. Set the time to midnight on both instances. Compare the skies.
   Note: you can make both screens clear by opening your chat.