I have found strange cf behaviour when the form contains an [select] fileld with "include_blank" parameter. Example form:
<p>Answer<br /> [select* your-answer include_blank "No" "Yes"]</p> <p>[submit "Send"]</p>
On page loaded, the blank element (---) preseted in the "your-answer" field. After clicking the "Send" button, i see the "Your message was sent successfully" box and the message is actually sent without error.
After clicking the "Send" button again the "strange behaviour" begins. The "your-answer" field clears (no item selected, must be "---" selected). The "spinning arrows" is spinning infinitely. No any error messages.
What expected: blank item must be selected into the "your-answer" field. Validation error tooltip and message must be shown.
Documentation and FAQ dont helps. Sorry for my english...