I have done a chat with you guys several times over the past week. I am having a problem with Hummingbird (v1.9.3) cache blocking the Quick Contact Form process on my site. This form is accessed via the white envelope icon on the bottom of every page of the site. Sometimes the form will work, but sometimes the user will complete the form, get a correct captcha, but clicking Send will not result in an “Email Sent” confirmation message. I’m concerned we are missing messages because of this since there is no clear indication to the site visitor that the message failed. Checking google console when I encounter this problem myself will show "Failed to load resource: the server responded with a status of 403 (forbidden) - "[site]/wp-admin/admin-ajax.php"). A temporary solution to this problem has been clearing the Hummingbird page cache. In my last conversation with you guys (chat tech was Rupok Chowdhury), he suspected that a cache was trying to serve a cached version of the ajax data associated with the form. After disabling another cache I had enabled, I still encountered the problem. Rupok requested that I disable Hummingbird caching and monitor the site/form for a day or so and contact you again. Since I’ve disabled Hummingbird caching on 1/9, I have tested the form repeatedly and have not encountered any problems. So I’m inclined to agree with Rupok that the Hummingbird cache is interfering with the ajax process. Rupok suggested there might be a way to exclude the form request from caching so we can use Hummingbird caching without losing the form feature.