Modal frame not scrollable on iPad

When a user clicks a modalframe 'create node' button, the resulting modal frame is not scrollable if the user is using an iPad. Instead, the underlying browser window scrolls.

If the 'Submit' button is placed off-screen, the user won't be able to submit the modal form and thus can't save their content.

I don't really know if this is a bug specifically with noderelationships, modalframe api or indeed with Safari on the iPad.