CloudFlare has an issue with you if you've previously failed human checks or are using a contained browser, with or without VPN and ad blocking extensions. They check your browsing history, and what other human checks you may or may not have failed, just by you using the internet. If they can't set a validation cookie for tracking you between other CloudFlare services, they may treat you as a bot and hang your connection.
I typically fail the "Select all the motorcycles" test because they show me scooters all the time. By doing that, my computer gets marked as suspicious, slowing down some of my connections that need to go through CloudFlare, sometimes just hanging my connection for a little time.
A serious question does arise, though. Have you tried using a regular chromium type browser to see its headers sent to CloudFlare to identify what might need to be sent?