We are running a small experiment where 0.3% of viewers will see an auto-generated thumbnail, instead of your custom thumbnail. We are not removing the ability to create your custom thumbnail, but we hope to gain insights on auto-generated thumbnails for the future.
Hey, this is part of the .3% saying this is GARBAGE! So many Youtubers work hard to make great thumbnails which I CAN'T SEE NOW! Wait, hold up, as I was writing this I can see thumbnails now. EVERYBODY AFFECTED BY THIS, COMPLAIN ABOUT IT.