I was about to report this but apparently, @11146 has found this bug too. Unlike 태암 김, I’m only experiencing it at the very first subtitle cell and in the YouTube version of Language Reactor.
The A [Previous], S [Repeat], & D [Next] keyboard shortcuts malfunction when we’re parked at the very first subtitle. Even the side buttons that do the same functions malfunction. Once we’re out of the first subtitle, they regain functionality. You can even A back to the very first but you can’t D to the second subtitle.