I typed a message to the manager of a certain profile, and I hit "Send" without showing that I was not a robot. I got an error message, went back and did what was needed. Now when I hit "Send", I got an error message saying that the message is empty. That is: the page forgot that I already typed the message in in the first round.
From then on it became impossible to send that message. I went through the correct operations needed to send, but the page remained in the state of an error and never recovered. I had to "Back" out and start the process from scratch.