When updating a sub-task in a Team-Managed Project through CSV import an error is thrown

Issue Summary

When updating a sub-task in a Team-Managed Project through CSV import an error is thrown using the External System Import.

Steps to Reproduce

1. Create a CSV to update any issue field in an existing sub-task
2. Choose the team-managed project where the sub-task is
3. Try to import CSV data through External System Import in https://site.atlassian.net/secure/admin/ExternalImport1.jspa

Expected Results

The desired field gets updated in the sub-task issue

Actual Results

The following error is thrown:

Unexpected failure occurred. Importer will stop immediately. Data may be in an unstable state: Failed to remove subtasks [ISSUE-KEY] parents. A parent of a subtask cannot be removed.

Workaround

REST API can be used to update the field as well as Parent of sub-tasks in Team managed projects