I'd like to try and help you with your problem. I am experienced video editor, with big experience in Camtasia Studio and different video tools. Could you, please, share this broken video, so I'd try to recover it? I can't guarantee that I'll succeed, but I have a will to do it and really huge toolkit of different video programs on of which may help in this problem. Looking forward for your answer.
Best regards,
Nickolay.