Steps/models to reproduce:

install https://yggdrasil-network.github.io/about.html
install https://github.com/Akarin-project/Akarin
try join to server on yggdrasil ipv6
use /skin random_nick

Environment description

https://timings.aikar.co/?id=286d214fb1d446419331e5b7fc498e16

Error Log:

Hastebin / Gist link of the error (if any)

[13:00:35 WARN]: [ChangeSkin] Task #281 for ChangeSkin v3.0 generated an exception
com.comphenix.protocol.reflect.FieldAccessException: No field with type int exists in class PacketPlayOutRespawn.
        at com.comphenix.protocol.reflect.StructureModifier.writeInternal(StructureModifier.java:363) ~[?:?]
        at com.comphenix.protocol.reflect.StructureModifier.write(StructureModifier.java:343) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendPacketsSelf(SkinUpdater.java:169) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendUpdateSelf(SkinUpdater.java:121) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendUpdate(SkinUpdater.java:102) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.onInstantUpdate(SkinUpdater.java:94) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.run(SkinUpdater.java:80) ~[?:?]
        at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftTask.run(CraftTask.java:84) ~[akarin-1.13.2.jar:git-Akarin-"18cd8f6"]
        at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:449) ~[akarin-1.13.2.jar:git-Akarin-"18cd8f6"]
        at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:1015) ~[akarin-1.13.2.jar:git-Akarin-"18cd8f6"]
        at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:440) ~[akarin-1.13.2.jar:git-Akarin-"18cd8f6"]
        at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:945) ~[akarin-1.13.2.jar:git-Akarin-"18cd8f6"]
        at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:842) ~[akarin-1.13.2.jar:git-Akarin-"18cd8f6"]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_201]

Configuration:

Hastebin / Gist link of your config.yml file

default config

confirmed on Spigot 1.13.2 / Java 12 openJDK / windows 64bit

`
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.comphenix.net.sf.cglib.core.ReflectUtils$1 (file:/D:/games/MineCraft_Server/build_server_1.13.2/plugins/ProtocolLib.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byt
e[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of com.comphenix.net.sf.cglib.core.ReflectUtils$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

[00:02:37 WARN]: [ChangeSkin] Task #249 for ChangeSkin v3.0 generated an exception
com.comphenix.protocol.reflect.FieldAccessException: No field with type int exists in class PacketPlayOutRespawn.
at com.comphenix.protocol.reflect.StructureModifier.writeInternal(StructureModifier.java:363) ~[?:?]
at com.comphenix.protocol.reflect.StructureModifier.write(StructureModifier.java:343) ~[?:?]
at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendPacketsSelf(SkinUpdater.java:169) ~[?:?]
at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendUpdateSelf(SkinUpdater.java:121) ~[?:?]
at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendUpdate(SkinUpdater.java:102) ~[?:?]
at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.onInstantUpdate(SkinUpdater.java:94) ~[?:?]
at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.run(SkinUpdater.java:80) ~[?:?]
at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot-1.13.2.jar:git-Spigot-f09662d-51d62de]
at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:392) [spigot-1.13.2.jar:git-Spigot-f09662d-51d62de]
at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:889) [spigot-1.13.2.jar:git-Spigot-f09662d-51d62de]
at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:417) [spigot-1.13.2.jar:git-Spigot-f09662d-51d62de]
at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:831) [spigot-1.13.2.jar:git-Spigot-f09662d-51d62de]
at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:729) [spigot-1.13.2.jar:git-Spigot-f09662d-51d62de]
at java.lang.Thread.run(Thread.java:835) [?:?]

`

Happens also in Spigot-1eece4f-84400e6 (MC: 1.14), latest ProtocolLib v4.5.0-SNAPSHOT from gradle branch and ChangeSkin v3.1-SNAPSHOT-bece00f.

[22:56:58] [Server thread/WARN]: [ChangeSkin] Task #27 for ChangeSkin v3.1-SNAPSHOT-bece00f generated an exception com.comphenix.protocol.reflect.FieldAccessException: No field with type net.minecraft.server.v1_14_R1.EnumDifficulty exists in class PacketPlayOutRespawn. at com.comphenix.protocol.reflect.StructureModifier.writeInternal(StructureModifier.java:363) ~[?:?] at com.comphenix.protocol.reflect.StructureModifier.write(StructureModifier.java:343) ~[?:?] at com.github.games647.changeskin.bukkit.task.SkinApplier.createRespawnPacket(SkinApplier.java:222) ~[?:?] at com.github.games647.changeskin.bukkit.task.SkinApplier.sendPacketsSelf(SkinApplier.java:164) ~[?:?] at com.github.games647.changeskin.bukkit.task.SkinApplier.sendUpdateSelf(SkinApplier.java:116) ~[?:?] at com.github.games647.changeskin.bukkit.task.SkinApplier.applyInstantUpdate(SkinApplier.java:86) ~[?:?] at com.github.games647.changeskin.core.shared.task.SharedApplier.applySkin(SharedApplier.java:27) ~[?:?] at com.github.games647.changeskin.bukkit.task.SkinApplier.run(SkinApplier.java:74) ~[?:?] at org.bukkit.craftbukkit.v1_14_R1.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot-1.14.jar:git-Spigot-1eece4f-84400e6] at org.bukkit.craftbukkit.v1_14_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:394) [spigot-1.14.jar:git-Spigot-1eece4f-84400e6] at net.minecraft.server.v1_14_R1.MinecraftServer.b(MinecraftServer.java:1009) [spigot-1.14.jar:git-Spigot-1eece4f-84400e6] at net.minecraft.server.v1_14_R1.DedicatedServer.b(DedicatedServer.java:396) [spigot-1.14.jar:git-Spigot-1eece4f-84400e6] at net.minecraft.server.v1_14_R1.MinecraftServer.a(MinecraftServer.java:957) [spigot-1.14.jar:git-Spigot-1eece4f-84400e6] at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:802) [spigot-1.14.jar:git-Spigot-1eece4f-84400e6] at java.lang.Thread.run(Thread.java:835) [?:?]

I think skin changes now, but only the exception is generated.

Hmm it seems that CodeMC Jenkins build fails, soo the version is not the latest one with commit 61ed9f0 from github.

Will wait for Jenkins to be fixed and will try again. :)

EDIT: With ChangeSkin v3.1-SNAPSHOT-32931e2 from Jenkins there are no more exceptions shown and skins are changing.

@KonoromiHimaries
@Martin-H2
@CommanderTvis

Duplicate of #153 - fixed a long time ago.

@mirolm New bug that occurred in 1.14. Fixed in e48d958. You can look at the development builds for a fixed version. (Sorry missed your edit)

Confirmed on Ubuntu (Liberica JDK 8u212) (latest release from spigotmc)

[09:41:04 WARN]: [ChangeSkin] Task #48 for ChangeSkin v3.0 generated an exception
com.comphenix.protocol.reflect.FieldAccessException: No field with type int exists in class PacketPlayOutRespawn.
        at com.comphenix.protocol.reflect.StructureModifier.writeInternal(StructureModifier.java:363) ~[?:?]
        at com.comphenix.protocol.reflect.StructureModifier.write(StructureModifier.java:343) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendPacketsSelf(SkinUpdater.java:169) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendUpdateSelf(SkinUpdater.java:121) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.sendUpdate(SkinUpdater.java:102) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.onInstantUpdate(SkinUpdater.java:94) ~[?:?]
        at com.github.games647.changeskin.bukkit.tasks.SkinUpdater.run(SkinUpdater.java:80) ~[?:?]
        at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftTask.run(CraftTask.java:81) ~[core.jar:git-Spigot-1a3504a-dfa7583]
        at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:392) [core.jar:git-Spigot-1a3504a-dfa7583]
        at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:889) [core.jar:git-Spigot-1a3504a-dfa7583]
        at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:417) [core.jar:git-Spigot-1a3504a-dfa7583]
        at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:831) [core.jar:git-Spigot-1a3504a-dfa7583]
        at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:729) [core.jar:git-Spigot-1a3504a-dfa7583]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]