@rx-3200 What do you mean?
what is your question about?
it = this build
slideshow = showing a few frames and freezing, then a few more frames and freezing, and so on in a circle (the viewing indicator under the video shows that the buffer is not empty, and 64.0.3417.119 plays the same video quite well)
on youtube = video on youtube.com
downgraded to 64 = overwrite the contents of the folder 64.0.3417.119 to the folder 67.0.3575.31, and use it again