Are you facing the problem that when you filter the result, and clear the filter, then you found your rows are same? Or are you facing this problem when you go to next page, and went back to previous page?

This problem maybe is because you have another primary id than what magento usually used, that is entity_id. So you need to replace the primary id to your primary id on your listing xml and inside your data provider syntax. e.g. I have primary id named example_id, so I need to add storageConfig>indexField and the value is my primary id which is example_id.

<argument name="data" xsi:type="array">
    <item name="config" xsi:type="array">
        ............
        <item name="storageConfig" xsi:type="array">
            <item name="indexField" xsi:type="string">example_id</item>
        </item>
        ............
    </item>
</argument>

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And for my example above, my grid will be like this : (after I went to page 2 and go back to page 1)

Page 2

Page 1