It said to report it, so I am! :)
It's a problem with Jade Integration through your mod. The screenshots from on a clean client with only Cobblemon, Cobblemon Integrations, Jade, and Fabric API on it.

This should be fixed with 0b511da. This was caused by Cobblemon 1.5.0 -> 1.5.2. This will be resolved in the next version (should be 1.0.6).

I'm having this issue as well and I would like to add that sometimes it causes the chunk that the fossil setup is in plus a few surrounding chunks facing east to not load blocks at all and only load entities. Below is a screenshot of my modded world where this is happening. I do have a lot of other mods installed, although I am certain its the fossil setup because I had this problem in a different part of my world and removing the setup fixed it. Now that its in my warehouse, the issue is back in that area of my world.

@Baboobraz Please let me know if this still occurs in version 1.0.6 (and isolate to confirm my mod is responsible).