Can't read data in Node-RED, port gets closed upon first input

Summary of Problem

I use the code in an ordinary js-file. There it runs as intended. When integrating the code into a Node-RED node, code fails. Writing data out of node red works.

(Please answer all 3)

What are you trying to do? Read data from serial input
What happens? Serial port gets closed upon the first arriving character/data over serial.
What should have happened? Transmitted data should be logged on console

Code to Reproduce the Issue

Working single Node.js code.

var SerialPort = require('serialport')
const ByteLengthParser = require('@serialport/parser-byte-length')

port = new SerialPort("/dev/serial0", { baudRate: 9600 })
port.on('error', function (err) {
  console.log(`Error: ${err.message}`)})

function showPortOpen() {
  console.log('port open. Data rate: ' + port.baudRate);
}

function showPortClose() {
  console.log('port closed.');
}

function showError(error) {
  console.log('Serial port error: ' + error);
}

port.on('open', showPortOpen);
receivedData = Buffer.alloc(0)

const parser = port.pipe(new ByteLengthParser({length: 8}));
parser.on('data', function(data)
{
  console.log("ByteParser: " + data)
})

port.on('close', showPortClose);
port.on('error', showError);

Same code integrated to Node Red file:

File: testnode.js

var SerialPort = require('serialport')
const ByteLengthParser = require('@serialport/parser-byte-length')

module.exports = function (RED) {
    function testnode(config) {
        RED.nodes.createNode(this, config);
        var node = this;

        node.port = new SerialPort(config.serialport, { baudRate: 9600 })
        node.port.on('error', function (err) {
            node.error(`Error: ${err.message}`)
        })

        function showPortOpen() {
            console.log('port open. Data rate: ' + node.port.baudRate);
        }

        node.port.on('open', showPortOpen);

        function showPortClose() {
            console.log('port closed.');
        }

        node.parser = node.port.pipe(new ByteLengthParser({ length: 8 }));
        node.parser.on('data', function (data) {
            console.log("ByteParser: " + data)
        })

        node.port.on('close', showPortClose);

        node.on('input', function (msg, send, done) {
            send = send || function () { node.send.apply(node, arguments) }
            node.port.write("test");
            msg.payload = "test";

            send(msg);

            if (done) {
                done();
            }

        });

        node.on('close', function () {
            node.port.close();
        });
    }
    RED.nodes.registerType("testnode", testnode);
}

When you want to try it. File testnode.html

<script type="text/javascript">
    RED.nodes.registerType('testnode',{
        category: 'testnode',
        color: '#04b50f',
        defaults: {
            name: {value:"testnode"},
            serialport: {value: "/dev/serial0"}
        },
        inputs:1,
        outputs:1,
        icon: "font-awesome/fa-arrow-right ",
        label: function() {
            return this.name||"testnode";
        }
    });
</script>

<script type="text/html" data-template-name="testnode">
    <div class="form-row">
        <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
        <input type="text" id="node-input-name" placeholder="Name">
    </div>
     <div class="form-row">
        <label for="node-input-serialport"><i class="fa fa-tag"></i> Serialport</label>
        <input type="text" id="node-input-serialport" placeholder="/dev/serial0">
    </div>
</script>

<script type="text/html" data-help-name="testnode">
    <p>This node reads the CO2 value of the MH-Z19 CO2 Sensor</p>
</script>

and package.json

{
  "name": "node-red-test",
  "version": "1.0.0",
  "description": "test",
  "main": "testnode.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "node-red"
  ],
  "dependencies": {
    "serialport": "^9.0.2"
  },
  "node-red": {
    "nodes": {
      "testnode": "testnode.js"
    }
  },
  "author": "test",
  "license": "MIT",
  "bugs": {
    "url": ""
  },
  "homepage": ""
}

when starting it in Node Red with 'export DEBUG=serialport/*' I get this errormessages.

serialport/bindings/poller received "readable" +9s
  serialport/bindings/unixRead Starting read +9s
  serialport/bindings/unixRead Finished read undefined bytes +1ms
  serialport/stream binding.read finished { bytesRead: undefined } +10s
  serialport/stream _read reading { start: NaN, toRead: NaN } +1ms
  serialport/stream binding.read error TypeError: "offset" is not an integer got "NaN"
    at LinuxBinding.read (/home/pi/node-red-test/node_modules/@serialport/binding-abstract/lib/index.js:89:13)
    at LinuxBinding.read (/home/pi/node-red-test/node_modules/@serialport/bindings/lib/linux.js:63:17)
    at SerialPort._read (/home/pi/node-red-test/node_modules/@serialport/stream/lib/index.js:375:16)
    at SerialPort.Readable.read (_stream_readable.js:470:10)
    at maybeReadMore_ (_stream_readable.js:618:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) +2ms
  serialport/stream disconnected TypeError: "offset" is not an integer got "NaN"
    at LinuxBinding.read (/home/pi/node-red-test/node_modules/@serialport/binding-abstract/lib/index.js:89:13)
    at LinuxBinding.read (/home/pi/node-red-test/node_modules/@serialport/bindings/lib/linux.js:63:17)
    at SerialPort._read (/home/pi/node-red-test/node_modules/@serialport/stream/lib/index.js:375:16)
    at SerialPort.Readable.read (_stream_readable.js:470:10)
    at maybeReadMore_ (_stream_readable.js:618:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) +12ms
  serialport/stream #close +2ms
  serialport/binding-abstract close +10s
  serialport/stream _read queueing _read for after open +1ms
  serialport/bindings/poller Stopping poller +21ms
  serialport/bindings/poller Destroying poller +1ms
  serialport/stream binding.close finished +3ms

Versions, Operating System and Hardware

SerialPort@? 9.0.2
Node.js v? 12.19.1
Windows? Linux? Mac? Linux
Hardware and chipset? (Prolific/FTDI/Other) Rasperry PI4

I don't know whats wrong here. Am I doing something wrong? Is it a bug in serialport? Hope you can help me.

serialport / node-serialport