Form getting cut off on website

I have two forms used on two different websites that keep getting cut off. If I refresh my page, it usually shows the whole form. How can I fix this?

https://www.hollyavenuedesigns.com/payment

https://www.ourchosenchild.com/make-a-payment

To fix that, please increase the height of your iFrame embed code:

You can set the height from 954px to 1050px to show all the content of your form.