@TeamYouTube Non-urgent, but one of my videos recently borked up pretty bad and wasn't posted to sub feeds (or even to my "posted" feed), and the thumbnail is the broken video image everywhere except my dash: https://youtu.be/qcUO0p7VIt4 (notes on what I've tried to fix it in reply)
Appreciate your efforts! Our Creator Support can dive into this further with you, get in touch here: https://goo.gl/BxLi8H . Hope this gets resolved.