is it possible to fix error The encoded data was not valid for encoding utf-8 in nodejs

I am tried to add subdocument https://docs.yjs.dev/api/subdocuments in the yjs sync server side code. when I tried to read content from uint8array like this(this code come from this discuss https://discuss.yjs.dev/t/extend-y-websocket-provider-to-support-sub-docs-synchronization-in-one-websocket-connection/1294):

const preHandleSubDoc = (
  message: Uint8Array,
  conn: Socket,
  targetDoc: WSSharedDoc,
  doc: WSSharedDoc
) => {
  try {
    const subDocDecoder = decoding.createDecoder(message);
    const subDocMessageType: number = decoding.readVarUint(subDocDecoder);
    const docGuid = decoding.readVarString(subDocDecoder);
    if (docGuid !== doc.name) {
      logger.warn(
        "this is an subdocument,subDocMessageType:" +
          subDocMessageType +
          ",doc guid:" +
          docGuid
      );
      handleSubDoc(targetDoc, docGuid, conn, doc);
    }
  } catch (err) {
    logger.error(
      "handle sub doc facing issue" +
        ", msg: " +
        Buffer.from(message).toString("base64"),
      err
    );
  }
};

shows error The encoded data was not valid for encoding utf-8:

// @ts-ignore
import encoding from "lib0/dist/encoding.cjs";
// @ts-ignore
import decoding from "lib0/dist/decoding.cjs";
function base64ToUint8Array(base64String) {
    const buffer = Buffer.from(base64String, 'base64');
    return new Uint8Array(buffer);
  }

const func = () => {
    const b64 ="AAG9AQADxLmwsQgJAB8gHT8dXgloCnUCeAGnAdUCjwQB7cvFkAYCAAQKAaW8jTgxAARPCmownAEoxwEBywEv/AEJhgI3wAIf4QJCpgMBqQMBrAMZ6wMB7QMB7wMBgwSnA/8JNbYKRv4KAoELEJMLJb8LAcELHeALEPILJ6AMF7kMEMsMJ/QMAfYMQ7sNJ+QNCe4NAfANKJoOAZwOHrwOFtQOEOYOFv4OH58PAqIPGb0PBcMPPIEQJ6oQAq0QFsUQAQ==";
    const message = base64ToUint8Array(b64);
    const decoder = decoding.createDecoder(message);
    const subDocMessageType: number = decoding.readVarUint(decoder);
    const docGuid = decoding.readVarString(decoder);
    console.log(docGuid);
}


func();

some update message pass but some messages shows error The encoded data was not valid for encoding utf-8. I have made a minimal reproduce code:

Uncaught TypeError TypeError [ERR_ENCODING_INVALID_ENCODED_DATA]: The encoded data was not valid for encoding utf-8
    at __node_internal_captureLargerStackTrace (<node_internals>/internal/errors:464:5)
    at NodeError (<node_internals>/internal/errors:371:5)
    at decode (<node_internals>/internal/encoding:429:15)
    at _readVarStringNative (/Users/xiaoqiangjiang/source/reddwarf/backend/yjs-explore/node_modules/.pnpm/[email protected]/node_modules/lib0/dist/decoding-2c98f95d.cjs:376:45)
    at func (/Users/xiaoqiangjiang/source/reddwarf/backend/yjs-explore/src/decode/utf8_decode.ts:16:30)
    at <anonymous> (/Users/xiaoqiangjiang/source/reddwarf/backend/yjs-explore/src/decode/utf8_decode.ts:21:1)
    at run (<node_internals>/internal/modules/esm/module_job:197:25)
    --- async function ---
    at runMainESM (<node_internals>/internal/modules/run_main:51:21)
    at executeUserEntryPoint (<node_internals>/internal/modules/run_main:74:5)
    at <anonymous> (<node_internals>/internal/main/run_main_module:17:47)
decoding-2c98f95d.cjs:376
No debugger available, can not send 'variables'
Process exited with code 1

this is the package.json:

{
  "name": "texhub-broadcast",
  "version": "1.0.29",
  "description": "",
  "type": "module",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1",
    "lint": "eslint --fix",
    "dev-node": "export NODE_ENV=dev && ts-node --esm src/index.ts",
    "dev": "vite --host=0.0.0.0 --port=3003",
    "build": "tsc"
  },
  "exports": {
    ".": {
      "import": "./dist/app.js"
    }
  },
  "dependencies": {
    "@babel/runtime": "^7.26.10",
    "@codemirror/state": "^6.5.2",
    "@codemirror/view": "^6.36.4",
    "@uiw/react-split": "^5.9.3",
    "dotenv": "^16.4.7",
    "lib0": "^0.2.99",
    "pg": "^8.14.1",
    "react": "^18.3.1",
    "react-dom": "^18.3.1",
    "react-split": "^2.0.14",
    "socket.io-client": "^4.8.1",
    "texhub-broadcast": "1.0.41",
    "typescript": "^5.8.2",
    "vite": "^5.4.14",
    "vite-plugin-svgr": "^4.3.0",
    "vite-plugin-top-level-await": "^1.5.0",
    "vite-plugin-wasm": "^3.4.1",
    "web-vitals": "^2.1.4",
    "y-codemirror.next": "^0.3.5",
    "y-protocols": "^1.0.6",
    "yjs": "^13.6.24"
  },
  "devDependencies": {
    "@types/node": "^22.13.10"
  }
}

why some message parse success but some message shows this error? what should I do to fixed this error?