When a nested modal is closed the .modal-open class is removed from the body even though a modal is still open, making it impossible to scroll to view the rest of the modal or press a cancel or save button.

I've replicated this through the following submenus/modals in the admin portal:
and in the following browsers / OSs
My workaround for this at the moment is to zoom out the view in Chrome to see the entire modal. My monitors here at work have a 1440 x 900 resolution, so I'm guessing this might not be noticeable for users with larger resolutions. Let me know if you need further information.
Ah - yep. Thanks for reporting this. I've run into this issue before but I'll have to spend a bit of time investigating a possible fix. Modal layering with bootstrap is tricky business (what year is it?!) so I'll have to do some digging to see if I can get this one knocked out.
All fixed! Let me know if you run into any issues.
Thanks for all of your hard work on this awesome project! 馃憤