Custom blocks disappear upon reloading a world.

I am currently facing a strange, unexplainable problem with an addon of mine: first of all, let us start by saying that i have recently updated a few custom blocks of mine that have never suffered from any kind of bug nor glitch with the previous versions of the game.. Up until now.

The problem being; each time i load a world with said addon, the blocks appear just fine in my inventory and i can use them with no problem whatsoever- BUT, as soon as i close that world and open it again, the blocks magically disappear from the world as if their files have never existed to begin with, the only way to fix it being relauncing the entire game every time i open a world with the addon; and even then, the fix is only temporary as the bug reappears once again as soon as i reload the world without restarting the game first.

I have personally double-checked all the files in my addon countless of times, furiously copying and pasting folders nonstop from older versions in a desperate attempt of fixing it, still nothing. It took me a while to even realize it wasn't my addon to begin with, but it's the game that got broken.

Nothing detrimental really- but it becomes pretty annoying having to remember the act of relaunching the game every time i hop off and on from my world, so any fix would be appreciated. My gratitude for any cooperation.

How to replicate:

1. Load up a world with any kind of addon that includes some sort of custom block.

2. Quit the world

3. Reload the world whilst keeping the addon loaded in it without closing the game

4. The blocks have completely disappeared from the world. Not a trace of their files left anywhere, not even in the functions or via commands.

Temporary fix:

1. Close the world after the blocks have been bugged

2. Reboot the game

3. Open your world again

4. The blocks are now back. As soon as the host closes the world, said blocks disappear from it until the game where the world is being hosted from is closed.