test:

src/jensen.js

@@ -717,8 +717,11 @@ Jensen.prototype.getFile = async function (filename, length, ondata, onprogress)
     let handler = (msg) => {
         if (msg != null) {
             flen += msg.body.length || msg.body.byteLength;
-            // const data = msg.body.join('').replace(/4869446F636B564D.*/, '').split('');
-            ondata(msg.body);
+            let hexString = Array.from(msg.body).map(b => b.toString(16).padStart(2, '0')).join('');
+            let regex = /4869446f636b564d.*/;
+            let result = hexString.replace(regex, '');
+            let data = new Uint8Array(result.match(/.{1,2}/g).map(byte => parseInt(byte, 16)));
+            ondata(data);
             // return OK indicates all file blocks received
             if (flen >= length) return 'OK';
         } else {