According to Oracle’s official documentation, ORA-39126 signifies that "An unhandled exception was detected internally within the worker process for the Data Pump job. This is an internal error". In essence, a slave process responsible for performing a subtask (unloading, transforming, or loading data) encountered an unexpected exception that the system’s internal exception handlers could not recover from.
Look for the last successfully processed object before the failure. Look for the last successfully processed object before
The user executing the Data Pump job may lack the necessary privileges. For example, the exporting user might not be able to read a dependent object referenced in a view's DDL, or a database link used in the job might be invalid. Object access is another common culprit; for instance, a job might fail when a target object has been dropped or a dependent object is in an invalid state. Object access is another common culprit; for instance,
The error code 71 is historically linked to spatial index or geometry validation issues. If your dump contains SDO_GEOMETRY columns and the target lacks Spatial components or has corrupted metadata, this error arises. Object access is another common culprit
Also, reduce the number of parallel workers:
Run a check on the target schema before restarting the import: