This has been happening for a while: once I upload a video to YouTube and go to editing, I can’t click play on “Ending Screen”" (thus can’t see where to start related videos, etc).
I’ve tried to disable Brave Shield but it still happens.
This may sound strange, but can you try uploading and altering the video in the same way you have been, but in a private window session and see if you get the same results?
Oh man, I’m so embarrassed… I’ve tried the private window session and them realized about that “view” (visualizar in PT-BR) button. I remember going to the Ending Screen and auto playing, so when that changed (maybe YouTube did), I thought it was Brave. Dammit it. Really sorry to waste your time.