Credit to DP for discovering it.

I was able to narrow it down to a specific line of code.

https://b.com/? [/quote=]
Originally posted by Celphi:
Test 
This code breaks div
https://b.com/? [/quote]
Originally posted by Celphi:
Test 
This code breaks div
https://b.com/? [/quote]
Originally posted by Celphi:
Test 
This code breaks div

Each line breaks the html container it is in.