The generated form contains the below control:
 
~~~
<input name="FilePath" type="file" class="form-control" id="field_4548" onchange="encodeImageFileAsURL(this);" required > 
~~~

The issue is in the "Kieserver-ui.js" file, in the "encodeImageFileAsUrl" function:
 
~~~
function encodeImageFileAsURL(input) {
var filesSelected = input.files;
 if (filesSelected.length > 0) {
 var fileToLoad = filesSelected[0];
 
 var fileInfo = {
 'name' : fileToLoad.name,
 'size' : fileToLoad.size,
 'data' : null
 };
 fileData.set(input.id, fileInfo);
 
 var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
 var local = fileLoadedEvent.target.result; // <--- data: base64
 var srcData = local.replace(/^data:.*\/.*;base64,/, "");
fileData.get(input.id).data = srcData;
 
 //console.log("Converted Base64 version is " + srcData);
 }
 fileReader.readAsDataURL(fileToLoad);
 } else {
 alert("Please select a file");
 }
}
~~~

It is getting hanged in the line (into the function(fileLoadedEvent) {...):

~~~
var srcData = local.replace(/^data:.*\/.*;base64,/, ""); 
~~~

Note: because of the issue RHPAM-3515, the customer had to modify the "function getData() {..." from String to Object:

~~~
<input name="FilePath" type="file" class="form-control" id="field_4548" onchange="encodeImageFileAsURL(this);" required >
 
 <script>
 function getData() { 
 return {
 'APManagerApprover' : String(document.getElementById('field_195248').value),
 'FilePath' : Object(getDocumentData('field_4548')),
 'Region' : String($('#field_6936').val()),
 'TeamName' : String($('#field_5422').val()),
 'MaterialsFromOtherTeamQuestion' : String($('#field_7898').val()),
 'ExternalMaterialsApprovedQuestion' : String($('#field_6426').val()),
 'ExternalMaterialsAsIsQuestion' : String($('#field_3585').val())
 }
 };
~~~