When loading the world border after loading a world and not moving at all, the border is occasionally rendered as a solid color or a gradient of different colors.
I've attached four screenshots demonstrating the issue.
- Create a new superflat world with "The Void" preset
- Run the command /worldborder center ~ ~ (Don't move after running this command!)
- Run the command /worldborder set 10
The border is shown as a solid color