Hello,
I had a chance to run this by the team that looks at Materials and relevant subsystems and they believe that this issue arises from the deserialization mismatches due to large difference in the engine versions. Further, they suggested that first migrating to 4.27(last UE4 version) and then migrating to UE5 might mitigate the issues. While this would be painful to migrate in steps, it will definitely help debugging the issue better.
If you get a chance to give it a try, and are still facing issues, please let me know.
Regards,
Vedang