Google temporarily disabled YouTube's advanced captions without warning
YouTubers have been increasingly frustrated with Google's management of the platform, with disinformation welcomed back and an aggressive push for more AI (except where Google doesn't like it). So it's no surprise that creators have been up in arms over the suspicious removal of YouTube's advanced SRV3 caption format. You don't have to worry too much just yet—Google says this is only temporary, and it's working on a fix for the underlying bug.
Google added support for this custom subtitle format around 2018...