CloudFlare offers a service called Rocketscript, which compresses, concatenates, and defers any JavaScript on your web pages. On some websites, it can make a significant difference to the apparent page load time, because it waits until the web browser has loaded the page before it loads and executes scripts. Of course, that sometimes means it breaks things!
Since Convert tracking script needs to start running on the same page time the page loads, to prevent any blinking effect, we recommend implementing the Convert tracking script without Rocketscript. That should fix the blinking issue.