Not sure if this is tied to issue #553, that is a gamerule blocking all spawns.

The issue I'm facing is that crocs are spawning in specifically desert, plains, and beach biomes when they shouldn't be. I honestly liked that they were spawning on beaches so I was focusing most of my testing on the other biomes. I have not seen any spawns outside of the overworld (like some old issues are reporting). From what I can tell, I was able to update the config to prevent spawns in rivers, but even if I add additional parameters specifically blocking desert and plains biomes they will still spawn. Maybe it's something to do when searching for a spawnable block for it? I've watched them spawn on grass and sand.

I've tested about a dozen different worlds and it consistently seems to only be these three biomes with the issue. It happens on fresh world spawns and with reloaded chunks after using kill all mobs command. I'm only running vanilla biomes with this pack. Below is one of the configs I've tried running with no changes in spawns (other than negate river true). I've also tried BIOME_DICT and BIOME_CATEGORY separately for desert with no change. ((sorry if this is not relevant I am new to this lol))

{
"biomes": [
[
{
"type": "BIOME_DICT",
"negate": false,
"value": "overworld"
},
{
"type": "BIOME_DICT",
"negate": false,
"value": "swamp"
}
],
[
{
"type": "BIOME_DICT",
"negate": false,
"value": "overworld"
},
{
"type": "BIOME_DICT",
"negate": true,
"value": "desert"
},
{
"type": "BIOME_CATEGORY",
"negate": true,
"value": "desert"
}
],
[
{
"type": "BIOME_DICT",
"negate": false,
"value": "overworld"
},
{
"type": "BIOME_DICT",
"negate": true,
"value": "plains"
}
],
[
{
"type": "BIOME_DICT",
"negate": false,
"value": "overworld"
},
{
"type": "BIOME_DICT",
"negate": true,
"value": "river"
},
{
"type": "BIOME_DICT",
"negate": true,
"value": "cold"
}
],
[
{
"type": "REGISTRY_NAME",
"negate": true,
"value": "biomesoplenty:tundra_bog"
}
],
[
{
"type": "REGISTRY_NAME",
"negate": false,
"value": "biomesoplenty:tropic_beach"
}
]
]
}

I have the same issue for all swamp mobs, i.e crocodiles, aligator snapping turtles and shoebills, I find them in some forests.

The same issue here, I found one in the end and a tundra.

I found a crocodile in the nether ;-;

It occurred to me later that I did have some mods that added additional nether mobs. Thinking maybe they taking up the spawn chances I made a separate vanilla instance with just AlexMobs and BadMods to remove all other nether mobs. I cranked up the spawn weight to 1000, spawn rolls at 1. Spent about an hour in maybe 8 different worlds and only found one croc in the nether, and I couldn't reproduce the spawn. Even though in the overworld I can reproduce spawns on basically the same blocks across world gens using the same seed. Either way, I think once the config for them is fixed it should resolve the nether/end spawns as well.

I also spent some time in the over world and found them in other biomes (several forest variants, savanna, etc).

I have found swamp mobs too, Shoebills (whatever they're called) in lakes/rivers and Crocodiles in a birch forest. (I died to them like 4-5 times-)

should be fixed