context.downloadAttachment( ) returning broken file object

Hi,

I’m building a plugin to save a message’s attachment and send it directly to a Google Drive. 

The problem I’m facing is that the context.downloadAttachment() function is returning a broken file: 

// attachments state contains message_id and attachment_id of all the conversation's attachments 

const handleAttachmentDownload = (index) => {
    context.downloadAttachment(
      attachments[index].messageData.id, 
      attachments[index].attachmentData.id
    )
    .then((resp) => {
      console.log(resp)
      setPreview(URL.createObjectURL(resp))
    });
  };

The promise is successfully returning a File

but as we try to handle the file (previewing or sending it to a google drive it for example) the resulting uploaded file is broken. 

Am I doing something wrong here? I’ve tested the exact same flow with a simple file input uploader and it works fine. 

Thanks