Cache bypassed on specific page

https://gainfutures.com/contact/live-chat always shows a BYPASS header, when using the URL tester in the plugin, or looking at the site in a private tab when not logged in.

The URL is not listed in the exclusions box.

Why else might this specific URL by bypassing the cache, when other pages on the site HIT it fine?

Note: The page itself does not contain live chat (it links to another service that does), so any efforts to be clever here based on the page slug isn’t helping.