Hello,
what happens if a dead dragon lays arround, (not the bones, just with skin).

can i fix this problem or is it a know bug?

It lays around with skin.

You just answered your own question.

I think the reason why the corpse is there is because the NPC's killed them and because there was no effort in you hurting the dragon you can't obtain their soul. But I also think it's a glitch too.