Spatial Anchor Does Not Load Entire Network

[5cript]

Describe the bug

I am on Neoforge 1.20.4

When I first placed the Spatial Anchor, it worked as expected.
Then I restarted the server and the Spatial Anchor shows:

Breaking and replacing it had no effect.

But! When placing it on a different cable (freshly connected to the controller) loads the chunks again:

Removing the block once more and putting it on the old cable yields the previous broken result.
Removing the block and putting it on the fresh cable / controller side yields the correct result again.

The issue persists through restarts and gets progressively worse, as I start to burn more and more sides I can connect it to.
Removing the cable entirely from the controller does not help, I need a new controller side. (what does this have to do with anything?)

How to reproduce the bug

See description

Expected behavior

At least breaking and replacing the block should get rid of the broken state.

Additional details

No response

Which minecraft version are you using?

1.20

On which mod loaders does it happen?

NeoForge

Crash log

https://github.com/user-attachments/files/16228207/latest.log

[shartte]

So I spent at least an hour investigating this only to arrive at the following conclusion:
The modpack you are playing is using something called "vanillafix" which completely breaks NeoForge chunkloading.
Please let the modpack maker know so they can remove it.