I thought it might be an extension[0], but its happening on chrome on my laptop too.
[0]: I had an idea to create an extension that hides every number >4 on the web, so that i am not bothered with "gamification".. but its not that
Because it's the first time it's happened.
TLDR Change resolution / screen size
Hope it is that easy for you, and it isn't a bigger problem.
This gave me trouble on my last job, a jira extension didn't work at 150%
(HAHAHAHAHA Jira.. i know)
Maybe something on YouTube got updated, and you were seeing some cached bit of code that didn't jibe right.
