This is the 13575th most frequent German word.
demselben
"The same" (dative case).
In this sentence, 'denselben' corresponds to 'the same' and is the accusative form relating to 'Fehler', showing sameness.
Wir haben denselben Fehler gemacht.
We made the same mistake.
Here, 'denselben' is used to indicate that the place I am thinking about is identical to another specified.
Ich denke an denselben Ort.
I am thinking about the same place.
In this example, 'demselben' is the dative form that aligns with 'Problem' and denotes sameness in the context of discussion.