When using the rendering feature "Chroma Keying" while having Shaders (Optifine) enabled, the sky gets weirdly static but not green, clouds get buggy and caves have weird green dots, shown in the example.mp4
w/ replaymod-1.16.4-2.5.2 & OptiFine_1.16.5_HD_U_G7, Tested with several Versions of Sildurs Vibrant and with a few other Shaders

Workaround for those experiencing the bug: Render your video twice, once with shader and without Chroma Keying and once without Shader and with Chroma Keying. depending on your editing software you can then either overlap them and use the chromakey of the one without shader on the one with (may search a tutorial or if it sounds to tricky maybe don't), reverse the chromakey (again depending on software) and put the green screen part over the shader video, or (the simplest solution) just fade to the one without shader when you want to chromakey, when you e.g. want to make a transition where you zoom into the sky this one is helpful. or replace your sky with a green one via texture pack and disable sun and moon - but not shure if that works. Hope I could help, in the end its not that big of an issue

shown in the example.mp4

where is the video?

https://youtu.be/VqbmD4_ffPY Video is to big

@RaderRMT heres the video

just noticed the same problem with those green dots with patches of water