I've made car model. I want to unwrap some details mesh. I've marked seams on all required (I think so) faces/places. Its my first so big model and unwrapping of so many faces. The result is strange:
It's my .blend file:
.blend file hyperlink
You have somehow managed to Pin some of the unwrapped vertices. That’s the red dots that appear in the UV editor. They are not really showing in the image you posted but show up in the .blend file you provided.
What you need to do is Unpin them and then UV unwrap again.