Hi,
Thanks for the update.
Was your Surface Duo ever enrolled in a work or school account, or managed by an organization (like Intune or MDM)? for now, please visit this tread, this is similar with your concern, this might help, here is the page: https://learn.microsoft.com/en-us/answers/questions/2308771/surface-duo-asking-for-lost-pin-after-factory-rese
Keep us updated by simply replying on this thread.
Kind regards,
Edward