A bug in After Effects with importing ProRes 4444 files with alpha
After Effects is not correctly interpreting the alpha Chanel of ProRes 4444 files - if there is an alpha fade in the imported 4444 video, a black shadow can be seen under the fade - this is the same whether premultiplied is selected or not. I have loaded the same files into Motion and Millumin and they work correctly. See the attached still - the text should be fading from transparent to white but is showing as transparent black during the fade.
This bug was fixed in After Effects 18.1
Can you please try this in the latest Beta build? I believe this issue is fixed already in Beta.