Minecraft 1.15.2
Forge 31.2.0
InControl 4.0.3
No other mods

Steps to reproduce:
Spawn.json:

[
	{
		"mindifficulty": 3.0
	}
]

All other .json files empty

Start minecraft, use the seed 2606377863908765435

Create world. It will freeze somewhere between 2% and 6%. It does not crash. At least on my system, it froze all 30 times I tested it (while reducing the test case), so you should be able to reproduce it too without issue.