Export & Import items missing on import filters checked

Hi There! I’ve started to use collection databases which I think is a great feature - I’m still learning and have therefore created several collections to see how it works. I had one original collection where I’ve added 95 items (rows) - I exported this file to a CSV and checked that I dont have any filters on so it should export ALL the data. When I imported it again - to create new collection, I’ve matched all the fields as required and imported it. BUT it then only imported 79 items…!? How does this work? I can not seem to find any info on how I should create /duplicate exact same collection and thought I could bypass this by exporting and importing it again.

I need this as there are pages that I need to connect to two different collections, some have more images than the other.

Your help will be so appreciated. Thank you.