So, if you try to send two messages with too little time apart from each other, the site will display an error - "Internal server error Flood detected". But, you will be completely locked out of posting, no matter how much time you wait before making the next post. The only way to be able to post again, is to solve the bypass captcha. But nowhere on the site does it tell you that, I have only discovered this by pure experimentation.
Maybe the error message should clarify that? Display something like "Internal server error Flood detected You have to solve the bypass captcha"