SK4 v4.2.2 crashes on SSP world-load ; `IllegalStateException: failed to create a child event loop`

[ASchneider-GitHub]

Bug Description

Attempting to launch a singleplayer world on a clean installation immediately crashes the game ### Did this behavior use to work in the previous version? I haven't played a previous version ## Steps to Reproduce (for bugs)

1. Download clean installation of SK4 v4.2.2
2. Launch game and create new SSP world with default settings
3. Game crashes while loading

Logs

• Client/Server Log:
• Crash Log: https://pastebin.com/sjeLMQUq

World Information

• World Preset: Sky Factory 4
• Prestige Enabled: Disabled
• Modpack Version world created in: v4.2.2
• Additional Content Installed: N/A

Client Information

• Modpack Version: 4.2.2
• Java Version: 16.0.1.0 (64-Bit)
• Launcher Used: CurseForge
• Memory Allocated: 8GB
• Server/LAN/Single Player: Singleplayer (no LAN)
• Optifine Installed: No
• Shaders Enabled: No

[sam-kirby]

This looks to be a vanilla Minecraft issue: https://bugs.mojang.com/browse/MC-34749

Either your security software is causing the crash, or Minecraft is unable to establish an internet connection over IPv6.

[ASchneider-GitHub]

Makes sense. The PC runs over an IPv4 VPN tunnel, so IPv6 is likely blocked. Guess I'll try forcing it to run on IPv4 with -Djava.net.preferIPv4Stack=true or disabling the VPN

[sam-kirby]

You could also try turning off DHCPv6 on your router if possible. It won't make an attempt to connect over IPv6 if your system does not have a v6 address.