Pack version 1.3
Optifne version 1.16.5_HD_U_G6
PlanetSkyOverride = false
How to reproduce?
-Select any shader pack, and wait for it to happen.

I don't want to be that guy, but this issue was raised and pinned already. #25

This is an issue with Optifine, and not something that can be fixed. Optifine is not officially supported.