It's on line 1924. log

The server uses Velocity's default connection to a Paper server, and when I switch to the Fabric server, I get the following error message: "Client disconnected with reason: Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(16397) + length(1) exceeds writerIndex(16397): PooledUnsafeDirectByteBuf(ridx: 16397, widx: 16397, cap: 16397)".

This is a list of server mods：
'[地形]ctov-3.4.2.jar.old' fabric-language-kotlin-1.10.19+kotlin.1.9.23.jar
'[地形]tectonic-fabric-1.20-v2.2.jar1' ForceAccessServer-forge-fabric-1.0.3.jar
'[地形]Terralith_1.20.4_v2.4.11_FABRIC.jar1' geckolib-fabric-1.20.4-4.4.4.jar
'[地形]Towns-and-Towers-1.12.0.jar.old' Jade-1.20.4-fabric-13.3.1.jar
'辅助alwaysawitherskull-1.20.4-3.2.jar' ledger-1.2.10.jar
'辅助moveboats-1.20.4-3.2.jar' ledger-databases-1.1.1.jar
'辅助cryingportals-1.20.4-2.7.jar' '[lib]collective-1.20.4-7.32.jar.old'
'辅助syncmatica-1.20.2-0.3.11.jar' '[lib]cristellib-1.2.4-fabric.jar'
'辅助Dynmap-3.7-beta-4-fabric-1.20.4.jar' '[lib]ctLibMod-0.0.15.jar'
'辅助quicksort-0.8.0+1.20.4.jar' '[lib]fabric-api-0.96.3+1.20.4.jar.old'
'辅助wanderingcollector-1.2.1+mc1.20.4.jar' '[lib]fabric-language-kotlin-1.10.18+kotlin.1.9.22.jar.old'
'辅助endportalrecipe-1.20.4-5.2.jar' '[lib]ForgeConfigAPIPort-v20.4.3-1.20.4-Fabric.jar'
'辅助invisibleframes-1.1.0+1.20.jar' '[lib]geckolib-fabric-1.20.4-4.4.2.jar.old'
'辅助slimyfloor-1.20-1.2.8.jar' '[lib]magiclib-all-0.7.398+fe2125a-stable.jar'
'辅助headindex-1.1.5.jar' PacketFixer-fabric-1.20.4-1.2.4.jar
'辅助servux-fabric-1.20.2-0.1.0.jar' quickshulker-1.4.0-1.20.jar
'[占位符互通]PAPIProxyBridge-1.5.jar' remote-inventory-1.20.2-1.3.jar
'[占位符]placeholder-api-2.3.0+1.20.3.jar' 'serverledger-1.2.10.jar.old'
'[carpet]carpet-extra-1.20.3-1.4.128.jar' 'serverlithium-fabric-mc1.20.4-0.12.1.jar'
'[carpet]carpet-org-addition-mc1.20.4-2402101556-1.23.0.jar.old' 'serverferritecore-6.0.3-fabric.jar'
'[carpet]carpet-tis-addition-mc1.20.4-v1.56.1.jar1' '[server]krypton-0.2.6.jar'
'[carpet]fabric-carpet-1.20.3-1.4.128+v231205.jar' '[server]lazydfu-0.1.3.jar'
'[carpet]gugle-carpet-addition-2.7.0-1.20.4.jar' '[server]MCDRcommandFabric-1.20.4-v1.2.1.jar'
'carpet-org-addition-mc1.20.4-2404061618-1.26.2 (1).jar' ServerReplay-1.0.7+mc1.20.4.jar.old
carpet-org-addition-mc1.20.4-2404061618-1.26.2.jar ServerReplay-1.0.8+mc1.20.4.jar
'[carpet]PluslsCarpetAddition-1.20.4-0.3.190+9e97daa-beta.jar' '[server]starlight-1.1.3+fabric.f5dcd1a.jar'
chesttracker-2.3.3+1.20.4.jar 'serverFabricProxy-Lite-2.7.0.jar'
Chunky-1.3.138.jar spark-1.10.58-fabric.jar
collective-1.20.4-7.40.jar t_and_t-1.12.1.1.jar
ctov-fabric-3.4.3.jar voicechat-fabric-1.20.4-2.5.16.jar.bak
fabric-api-0.96.11+1.20.4.jar XaerosWorldMap_1.38.1_Fabric_1.20.4.jar

I guess the problem is usually some stupid mod that miswrites ByteBuf.

English is not my native language and I may struggle to articulate myself effectively.

It seems that a mod called "ChatHeads" is your problem. You also have A LOT of Mixin Injection errors usually caused by having too many mods installed....

`
at dzwdz.chat_heads.ChatHeads$PlayerInfoCache.createNamesByFirstCharacterMap(ChatHeads.java:286) ~[%5B����ͷ��%5D%20chat_heads-0.12.0-fabric-1.20.3.jar:?]

net.minecraft.class_7594.handler$bom000$chat_heads$chatheads$handleAddedSystemMessage(class_7594.java:1045) ~[client-intermediary.jar:?]
`

no
Not the reason for this mod