There are certain limitaions with package converter prior to App-V 5.1.It will not convert scripts, packages with dependencies, and other certain customizations in the OSD file.
The new App-V 5.1 has more advantage in case of converting from earlier 4.6 version.
I am not sure about the failure in your case (LegacyException).Why not check for any scripts or dependency in the OSD files?If present remove them from the OSD, convert and then add them in the dynamic config file.
I would recommend re-sequencing using App- V 5.0 or 5.1 sequencer(which ever suits your environment) in case if there are no customizations in the OSD to avoid future failure of the application.
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