Outlook contact CSV import corrupts existing contacts without warning

Outlook (classic) corrupts existing contacts during CSV import without any warning.

When I re-import a CSV exported by Outlook itself (UTF-8 with BOM),

the contacts lose their names and email addresses and appear as

“Name not available”.

Using the exact same CSV content re-encoded as Shift-JIS imports correctly.

This behavior is reproducible and cannot be prevented by user actions.

It appears to be a defect or a flawed design in Outlook’s CSV import logic.

Please investigate and provide an official explanation.