unable to open zip after creating it

Question

Sorry in advance for the possible bad implementation, I just started studying javascript and Node after 10 years without coding.I did this with the use of chatgpt.

I'm trying to figure out how to properly write a zip file from a base64 payload received from a REST call.

request(options, function (error, response) {
          if (error) throw new Error(error);
          let testPath = folder + '/' + ts ;
          fs.mkdirSync(testPath, (err) => {
            if (err) {
              console.error('Error creating folder:', err);
            } else {
              console.log('Folder created successfully!');
            }
          });
          fs.writeFileSync(testPath + '/response.xml', response.body, (err) => {
            if (err) {
              console.error('Error saving response to XML file:', err);
              return;
            }
            console.log('Response saved to response.xml');
          });
          let parser = xml2js.Parser();
          parser.parseString(response.body, (parseErr, result) => {
            if (parseErr) {
              console.error("Error parsing response:", parseErr);
              return;
            }
          let parsedResult =  result;
          const payloadString = parsedResult.response.payload[0];
          console.log('payload is: ' + payloadString)
          // Decode the base64 payload
          const decodedPayload = Buffer.from(payloadString, 'base64');
          console.log('decoded is: ' + decodedPayload)

        fs.writeFileSync(testPath + '/payload.zip', decodedPayload, (err) => {
            if (err) {
            console.error('Error saving payload to ZIP file:', err);
            return;
            }
            console.log('Payload saved to ' + testPath + '/payload.zip');
        });
        
        // Add logging for debugging
        //console.log('Decoded Payload:', decodedPayload.toString()); // Log the decoded payload before writing to the zip file
        
        // Your existing code...
        
                console.log('Job_ID: ' + parsedResult.response.jobInfo[0].$.id +' for file ' + zipFilePath + ' and received a ' + response.statusCode); //logga job id , file usato e status code
                });
      });

this is what I get when I try to unzip the file:

diego@DESKTOP:/mnt/c/Users/diego/path/$ unzip payload.zip 
Archive:  payload.zip

caution:  zipfile comment truncated
error [payload.zip]:  missing 4030336493 bytes in zipfile
  (attempting to process anyway)
error [payload.zip]:  attempt to seek before beginning of zipfile
  (please check that you have transferred or created the zipfile in the
  appropriate BINARY mode and that you have compiled UnZip properly)

I tried logging everything to the console, i tried aswell to decode manually the base64 payload from base64guru and it returns a correct zip that I can access from my computer.

I also tried asking chatgpt but keeps telling me the same things and after trying over and over I'm stuck.

Thanks, Diego