The bounding box for structurs has disapeered

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I found a swamp hut a few weeks ago in my world. I started to mine around it and in one of the most recent updates, the swamp hut, as well as 2 outposts and a monument, no longer spawn any hostile mobs. i loaded the seed (1182924952) up on a new world and the structures are fine but on my world they do not exist. I used the locate command but they did not show up. The photos below are the new world and the old world on the same seed. At first the original did work and showed up on the /locate. Now it does not