ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 0 During Mod Loading

What the log looks like

java\.lang\.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 0
ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 0[\s\S]{0,250}dev\.architectury\.event\.EventFactory\$EventImpl\.register

How to fix it

1. Relaunch Minecraft once or twice first, as this crash is an intermittent thread race condition and the exact same modpack will often start cleanly on retry.
2. Look at the lines directly below `java.util.ArrayList.add` in your crash report; if `dev.architectury.event.EventFactory$EventImpl.register` appears, update Architectury API to the newest build for your Minecraft version.
3. Install or update ModernFix, which adds thread-safety workarounds for older mods (including Mowzie's Mobs, Twilight Forest, and Dungeons Gear) that trigger this crash during the `complete` event phase.
4. If the crash keeps happening on a multi-core PC and no mod update is available, open `config/fml.toml` in your instance folder and set `maxThreads = 1` to force single-threaded mod loading as a workaround.

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