User blog comment:Rappy 4187/Technical Update: March 10, 2015/@comment-452-20150312181303/@comment-452-20150313203559

It sounds like you've proven the problem is with third party scripts.

Part of the issue is likely to be that Chat.js is now loaded much earlier than it used to be - as you noticed, it's now doing things before the welcome message appears - and the people who wrote those scripts weren't expecting that, so had their scripts executing immediately instead of waiting for the rest of the chat to finish loading.

I had one such issue in one of my personal scripts, because I was adding a hook to mainRoom before mainRoom was defined. Luckily, that was only effecting me, and the same thing didn't happen in any of my other scripts, because they don't load and run until the chat is fully loaded anyway.