I have some saved transactions with valid XML, but whenever I attempt to resume from saved, I get an empty form.
The transaction has valid XML associated with it, but it's just not prefilling into the rendered form.
Also obtained from the save success page.
If you disable the "Include Open Saved Form Feature", it actually disables the functionality to resume all together.
This options works differently to the equivalent Composer option, which just hides a section on the top of the form to "click here to open a previously saved form".
I understand that the Maestro team will soon change the way that this option behaves (or remove it all together).