Hello Sachita,
As the error message says, the data has entries that have a non-existent parent node. To debug that, I would recommend to:
1) Get all ParentIDs of all entries
2) Check if each of the ParentIDs have a corresponding item with ID equal to the ParentID
Once you do that, you should find which entries have non-existent parents and fix them.
Regards,
Peter Milchev
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