I had the same problem. I have 200 videos in my experiment. I had issue playing videos if I load all 200 videos but no problem at all if I shorten my experiment to only 40 videos.
It seemed that this was due to the recent update of Chrome which limited the number of web media players. Here is a relevant topic: Chromium, Chrome, Edge version 90 and more limits number of opened MediaPlayers
Also see the thread here: google chrome - Blocked attempt to create a WebMediaPlayer as there are too many WebMediaPlayers already in existence - Stack Overflow
In this thread, it was suggested that Chrome will be raising the limit to 1,000 today (3rd of August). I’ve just updated my Chrome and retried my experiment and it seems work.