Do you really want to add this item? It looks like it already exists in your library. Smith, Joe. 2010. How to avoid duplicate entries. Ms., Amsterdam.[A] Cancel and go to similar item. [B] Add anyway.
If the process has a problem, as it has three times, duplicates very quickly build up.
The problem with duplicates is that there are a lot of non-trivial issues. We are using a group library for 12 people in the research group. If someone just deletes duplicates it will break many papers causing extra work and confusion for also other people besides the one that did the duplicate removal.If something "quick and dirty" is implemented now, it will most likely backfire by causing compatibility issues when users later migrate to a "more proper" duplicate detection.
We're not going to roll out duplicate detection that produces broken citation links when you actually use it.