Premier Pro duplicating items when adding them or moving to new bin

I'm having an 'issue' in Premier that is annoying me. I think I may have accidentaly hit a key bind or turned something on, but when moving an item into a new bin it creates a duplicate of the item within that bin, rather than just moving the original.

Can't seem to find anything online and as far as I can remember, and up to a couple days ago, my PrPro has never done this. How can I turn this off?

I'm using the latest version of Premier Pro Beta,

Thanks!