Instance with same Id created twice. #45

I have this fictional object graph with the following structure:

|- Master
    |-Details
        |-Childs

Master -> Detail 1..N
Detail -> Child 1..N

I have a query which returns a record set with 20 records containing

• one master (duplicated over all rows)
  • which has one detail (duplicated over all rows)
    • which has 20 childs (each row containing one child).

The query is executed via Dapper and returned as a dynamic.

So when I map this I expected to get one master object which has one detail object which has 20 child objects.

|- Master (1)
    |-Details (1)
        |-Childs (20)

What I actually get is one master with two detail objects where the first detail object has one child and the second detail object has 19 childs.

|- Master (1)
    |-Details (1)
        |-Childs (1)
    |-Details (1)
        |-Childs (19)

The properties including the Id of both detail objects are the same. On the image below you see an comparison of both detail objects.

The first row in the record set get's it's own detail object with one child. The second till the last row get's a shared detail object but shares the master object with the first detail object.

I've looked into the data and there is nothing wrong with it. What could be going wrong here?