The captcha changes constantly while filling the form.

I'm having the same issue on my customer's site. The captcha changes rapidly, constantly. If you put in a word, it'll bring up another captcha which is stable and you can type it in. Need to stop the constant cycling. My customer is getting a bit angry.

http://www.millenniumairship.com/invest.htm

I checked your embedded form on Chrome, Edge and Firefox. I didn't experience the issue on Chrome and Edge, but I did encounter it when viewing the form on Firefox.

There might be a script on the page that is causing the issue with the captcha. To resolve this, can you please try embedding the form to your website using the iFrame embed code? Here's how: Getting the form iFrame code.

If the issue persists, please let us know
Regards.