We attempted to migrate work items from one ADO instance to another. Most of the data was migrated successfully, except for the items mentioned in the issue title.
Regarding the discussion section, only the first comment was migrated; the remaining comments were uploaded as a .json file instead. Work item histories (i.e., ticket updates) were not migrated either. While parent/child relationships were migrated, they still reference the source ADO, which should not be the case.
It is currently unclear whether these issues are due to limitations of the migration tool or a misconfiguration during the migration process.