Media fields might not be updated when migrating blobs to Azure Blob Storage. Checking the Media field of media items using the /sitecore/admin/dbbrowser.aspx page shows that the GUID value of this field lacks the "blob://" prefix.
To resolve the issue:
INSERT INTO @BlobFields ([FieldId]) ( SELECT [ItemId] FROM [SharedFields] WHERE [FieldId] = 'FF8A2D01-8A77-4F1B-A966-65806993CD31' AND [Value] = '1' UNION SELECT [ItemId] FROM [VersionedFields] WHERE [FieldId] = 'FF8A2D01-8A77-4F1B-A966-65806993CD31' AND [Value] = '1' UNION SELECT [ItemId] FROM [UnversionedFields] WHERE [FieldId] = 'FF8A2D01-8A77-4F1B-A966-65806993CD31' AND [Value] = '1' UNION SELECT [ArchivalId] FROM [ArchivedFields] WHERE [FieldId] = 'FF8A2D01-8A77-4F1B-A966-65806993CD31' AND [Value] = '1' );
with the following code:
INSERT INTO @BlobFields ([FieldId]) VALUES ('{40E50ED9-BA07-4702-992E-A912738D32DC}'), ('{DBBE7D99-1388-4357-BB34-AD71EDF18ED3}');