Error during import contacts - The duplicates are not detected


An error is displayed when importing contacts (see image)
Inkederreur import_LI

But despite this, the contacts are still imported.
But the duplicates are not detected, could this be the cause?

Thank you for your help.

I would start with disabling the notices (->php.ini), maybe that already solves your problem (not sure about that - usually, you can modify during the import how duplicates are defined).