We've implemented a fix and entries are going through. Systems are currently being monitored and slowly being brought up to scale, so things might take a little longer than usual.
You might still see these two kinds of error messages:
Security header check failed: It happens when we make a change. Please refresh the page and try again.
Sorry, you tried to enter too recently. Please try again in a few minutes: We are currently rate limiting to lower the number of requests to Twitter. Please try again in a few minutes.