Pre 1.3 I used dragon lairs for soul farming and iirc after 1.3 Bethesda changed it so you can no longer do that. It may be something related to that. Did you kill a dragon at a lair you had previously cleared?
I dont have ANY patches
and ive killed about 5 respawning dragons passing by their lairs or getting a quest to go back up to an area i had cleared a week before
one that wont decay i found in middle of no where near a giant camp
Edit: make that the one that found me