I am getting an Internal Error when running Validate.
First, make a new backup of your broken data as it currently exists. When you attempt to run Validate again, see if you can read the status messages that are being displayed at the bottom of the screen as Validate runs. See if you can read the last one that is displayed before the crash. If we can figure out what MYM is validating when it crashes, we can narrow down where the corrupted data exists.