CAPTCHA Security is a built in self defect mechanism in the App to prevent abusive use of the service (like being used by bots).
If you get the CAPTCHA prompt, that means you've been creating files too quickly or have been updating a file many times within a short period.
In such case, please slow down. Or, finish your current file and take a break before you start creating your next file.
If still you are getting a CAPTCHA prompt on each file creation, please clear cache, delete cookies of your browser and re-login.