Same thing for me. I installed a 5506-X for a customer on fairly new ASA code with a recent ASDM version but it freezes at 77%. I tested in a lab environment (real hardware) the most recent ASA code with recent ASDM and it worked fine. I then tested in my home lab (ASAv) but used the customer's config and I ran into the same issue again. I think it is something in the config that is freezing it at 77%.
I would REALLY like to have a fix for this. Cisco sells us this garbage but when I can't get it to work I have no TAC support.