GrabzIt doesn't screenshot whole page

None of my pages on my site https://academy.brain-power.com are being captured properly. The resulting screenshot shows only the top of the page, but not anything below. It's as if GrabzIt cannot scroll down to see the whole page.

Here is the site:

https://academy.brain-power.com/

Here are some pages on the site that don't capture properly:

https://academy.brain-power.com/

https://academy.brain-power.com/azpe

https://academy.brain-power.com/nelms

Unfortunatley, as this website uses a scroll bar in a div to scroll all of its content we can't capture a full page screenshot as it isn't possible to calculate its true size.

Of course if you specify its size it will work.