prob with formData -> Fetch

Question

I know this question is frequent but I can't find the right solution reading all the posts about Fetch and formData :

I have a lot of pseudo-forms written in JS in different divs to load images using a unique common function

 function uploadImage(ref,rep,int,num,typ,div){  
    
 let form = '<span class="uploader">';
     form+= '<input id="rep-'+num+'" value="'+rep+'"><br>'; // upload directory
     form+= '<input id="ref-'+num+'" value="'+ref+'"><br>'; // image name to use
     form+= '<input id="typ-'+num+'" value="'+typ+'"><br>'; // type of image
     form+= '<input id="div-'+num+'" value="'+div+'"><br>'; // where to display it once loaded on server
     form+= '<input type="file" class="fileimg" id="file-'+num+'">';
     form+= '<button onclick="saveImage('+num+')">'+int+'</button>'; 
     form+= '</span>';
    
     return form
 }

the code calling the function for 1st picture:

 document.getElementById('img-1').innerHTML = uploadImage('name-of-the-image','dir-to-put-the-file/','ADD AN IMAGE HERE',1,0,'img-1'));  

and now the JS to fetch img to server:

 function saveImage(n) {

   let rep = document.getElementById('rep-'+n).value, // dir
       ref = document.getElementById('ref-'+n).value, // name
       typ = document.getElementById('typ-'+n).value, // type
       div = document.getElementById('div-'+n).value; // div.id

   const url = "upload-imgs.php?imgname="+ref+"&directory="+rep+"&typeimg="+typ
   const files = document.querySelector('[type=file]').files;
   formData = new FormData();

   for (let i = 0; i < files.length; i++) {
      let file = files[i];
      console.log('FILE = '+file.name);
      formData.append('image', file);
   }

   fetch(url, {
      method: 'POST',
      body: formData
   }).then(response => {
      if( response.status==200 && response.ok == true) {
        return response.text().then( text => displayIf(text) )
      }
   });

 }

PHP write the image with the right name at the right place dependind the right type of image (photo, graph, plan, ...) then return echo $dir.$new_name and the function displayIt(img) shows the new image in the right div

It works perfectly but only for the first image loaded. I think the prob is coming from formData which is to reset, but despite testing different possibilities I cant't find the right one:

    if( response.status==200 && response.ok == true) {
        return response.text().then( text => displayIt(text) )
        formData.delete('image'); // log :  unreachable code after return statement
    }

Adding formData.reset() instead, or in the displayIt(img) function, doesn't solve the prob: same log. Where am I wrong?