crash message: The game crashed whilst exception generating new chunk
Error: java.lang.IllegalStateException: Unknown biome id emitted by layers: 260
Exit Code: -1
crash-2021-03-11_15.28.42-server.txt

In the config folder delete survivalisland.json or edit the startingBiome. Ecotones:Temperate_forest is no longer a biome and this was a very old config that Ak9 was messing with at some point. We will change this back to its default in the next update.
Here is the bad config.
{
"islandSize": 7,
"islandRarity": 6,
"startingBiome": "ecotones:temperate_forest",
"generateBeaches": true,
"seperateBiomes": true,
"hardcoreMode": true
}
This is the default config.
{
"islandSize": 5,
"islandRarity": 6,
"startingBiome": "minecraft:forest",
"generateBeaches": true,
"seperateBiomes": true,
"hardcoreMode": false
}

Just some more info. Player created a world in single player and played for about 5 hours. Crashed happened whenever they went North. I would have expected the game to crash right away since the biome doesn't exist but I suppose it actually started them in a different biome. Either way deleting the config or changing it to default fixed the issue. Leave this open until Ak9 fixes the config

no response from OP.. closing