PaperMC/paper-server/patches/sources/net/minecraft/network/protocol/PacketUtils.java.patch

--- a/net/minecraft/network/protocol/PacketUtils.java
+++ b/net/minecraft/network/protocol/PacketUtils.java
@@ -21,6 +_,7 @@
     public static <T extends PacketListener> void ensureRunningOnSameThread(Packet<T> packet, T processor, BlockableEventLoop<?> executor) throws RunningOnDifferentThreadException {
         if (!executor.isSameThread()) {
             executor.executeIfPossible(() -> {
+                if (processor instanceof net.minecraft.server.network.ServerCommonPacketListenerImpl serverCommonPacketListener && serverCommonPacketListener.processedDisconnect) return; // Paper - Don't handle sync packets for kicked players
                 if (processor.shouldHandleMessage(packet)) {
                     try {
                         packet.handle(processor);