Automatically changes the chat view to Live Chat when it loads. (Works with chat replays, too.)
< Feedback on YouTube - Enable Live Chat By Default
I've found it, it's the Super Fast Chat script. If I disable it, your script works correctly. I will contact the other dev.
Something should be changed in "YouTube Super Fast Chat" but still under investigation.
Thank you for the script. It works, but the chat (sometimes?) doesn't get populated after changing. Then it is empty and there's a blue "arrow down" button which I need to click to populate it.
I'm not sure at this point what the conditions are for it to work/not work, I will post it if I find out. It could be that your script is not the problem.
I'm also running the following userscripts by CY Fung:
Fix Brave Bug for YouTube Live Chat
YouTube Super Fast Chat