If I connect flying crystal to the lens, the game crashes with:
https://pastebin.com/MiRWyAED
The world becomes broken and I got this error every world load.

Looks like your lens has a bad NBT value, will need to use something like worldedit to remove the lens. How did you get the lens? How did you place it? Did you use something like building gadgets or the like on it at some point, which will strip the NBT?

I crafted it and placed it by hand

What pack, and what recipe? Not able to reproduce that normally.

Looks like your lens has a bad NBT value, will need to use something like worldedit to remove the lens.

Removing the lens won't stop the crashing, since the starlight network doesn't get updated.

Still has to be removed. If it still crashes on start AFTERWARD, will need to trigger the "rebuild starlight network" server config file option.

You can also just delete the starlight network for the chunk the lens is in. You don't need to edit out the lens that way.

What pack, and what recipe? Not able to reproduce that normally.

My own. Ther is mods list: https://pastebin.com/A6fbTaVi

To wrap this up and close it out: the NBT was stripped off the lens somehow. BuidlingGadgets is a common instance of seeing this, which can cause this.