Those objects should be checked individually to see what is causing the error. The Data correction should be done in the R12.0 SP3 Policy Store using the XPSTools from the Policy Server R12.0 SP3. By running XPSExplorer tool, you could check those objects and the value of the DomainLink attribute.
If DomainLink attribute is not correct (should point to a valid Domain XID), it may mean that the objects were corrupted or not removed correctly,
and this would need to be addressed manually in order to be imported successfully in the new Policy Store.
To lead a Policy Store integrity check, another option is to install a R12.6 Policy Server to use the integrity tools to repair those objects from the Policy Store 12.0SP3