Face is connected to other faces, cant delete

[max2]

Hi together,
can someone help me with this problem here. I’ve got a closed shape (see the L-shape in the screenshot), but its face is connected with the outer face. I can’t delete the L-shaped face alone.

I would assume that the problem is somehow that the L-shape is not really closed from its edges, but i couldn’t find anythin here…

Thanks for your help and best regards!

[Box]

Attach your model so we can find the problem.

[max2]

Sure, thanks for your fast response!
Attachtment deleted because problem solved. Contained private data.

[Box]

Just trace any edge.

[max2]

Awesome, that helped! Could you somehow explain why this is necessary? All edges are already there?

[Box]

Sometimes it just happens.