Applied Energistics 2 Server Startup Crash (WorldData IllegalArgumentException with SpongeForge)

What the log looks like

java\.lang\.IllegalArgumentException\s+at com\.google\.common\.base\.Preconditions\.checkArgument\(Preconditions\.java:\d+\)\s+at appeng\.core\.worlddata\.WorldData\.<init>\(WorldData\.java:\d+\)
at appeng\.core\.worlddata\.WorldData\.onServerAboutToStart\(WorldData\.java:\d+\)

How to fix it

1. Check your server's mods folder for SpongeForge (specifically builds around 1.12.2-2838-7.2.3) or check if you are running a Bukkit/Spigot hybrid server jar.
2. Update or downgrade SpongeForge to a different stable build (for example, moving off SpongeForge 7.2.3 to a newer 7.3.x or 7.4.x release) that resolves the world directory initialization bug.
3. If you do not strictly need Sponge plugins, remove the SpongeForge jar from your mods folder to run a standard Forge server, as Applied Energistics 2 does not officially support Sponge or Bukkit hybrids.
4. Restart the server and verify that the AE2 world data folder initializes cleanly.

Check your own log