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.