green dune
(This issue is a re-posting on Discord after seeing the pinned FAQ on the Steam discussion page, I can close the Steam bug post if needed)
Step 1. enter the pocket dimension and visit each of your creature pens (fish, Bubblebears, Fruit Femmes, Noots and Glaggles).
Step 2. go into the water around the Osmium pillar and continue swimming for a while, in my case I was trying to swim to the object in the screenshot which might just be backdrop so I gave up swimming for now.
Step 3. die and respawn back at the Osmium pillar.
Step 4. inspect each of your creature pens - they were previously full of creatures but now are all empty with no creatures inside and no drops indicating they were killed.
I had a few dozen passive creatures in my pocket dimension that were each inside of pens made on the side of the Osmium pillar. Those creatures would always be there when I'd travel the overworld and re-enter the pocket dimension.
But when I went swimming around the pocket dimension and returned back to it again, they had all been despawned.
Device info: Windows 11, RX 7900 XTX GPU, Ryzen 5 9600X CPU
World seed: cagey occur glossy
Version 2.8.7
subtle belfry