Follow the steps below to fix this error:
Remove all the dividends.
Manually add the details to clear the error message.
Given ExtRef GUID d4ed322f-aed8-46b6-b4e5-2b258be67b40 is already present in this document under class DividendIncomeSharingGridSelectorDocumentSelectorAutoGenExtRef error occurs when opening a tax return, and the tax return is then locked.
Follow the steps below to fix this error:
Remove all the dividends.
Manually add the details to clear the error message.