Hello Leonid, did you see the problem? That's what it looks like, it seems to be with firefox only, it seems to happen when the video in column number 2 and 3. That's why it's hard for you to arrive at the right time. (ff 66.0.4)
Hello Leonid, it looks like the latest version 66.0.5 finally corrects this problem, it's the first time it works well, it's nice! Maybe Genesis can confirm if it works for him too.