I am still somewhat mystified as to what you are doing ?

To be clear, I am talking about duplicates created when someone initially posts with an attachment and then others reply to it but *include* the attachment (I suspect (not so) smart phones are mostly to blame for this)

So the ones I would delete are copies of the attachment in the original post (which just take up storage room)

I have deleted many duplicates over a fair length of time and never has it deleted the original attachment

It sounds to me as if you are deleting a different attachment to the original

Nivard Ovington in Cornwall (UK)