Photos keeps importing "Already Imported" photos

The new Photos app [Version 1.0 (209.52.0)] keep recognising a few photos from my phone as 'New' even though it has already been imported (about 20 out of my 3000+ photos).

This also happens when importing photos from folders; it keeps identifying a few as 'New'.

I tried restarting the app and the computer but problem does not cease. Anyone else facing this problem and know how to rectify this?