Uploaded .doc/.xlsx files corrupted

Hey there!

A client’s website (currently running on Kirby 4.7) has a member’s section which they also exchange files with. The client is reporting that while this works perfectly for PDFs, many of the MS Word/Excel (.docx/.xlsx) they upload are corrupted once they download them again. I’ve tried downloading some of their .xlsx files and indeed couldn’t open them.
To clarify: The files are being uploaded directly through the panel, not via the frontend. The file template used does not specify a file type, since it is used for both PDFs and MS Word/Excel files. PDFs don’t seem to be affected by this issue; they open just fine.

Any idea what this could be caused by? Can this be a template issue?

This is the file template in question:

title: File
sortable: true

sections:
  general:
    type: fields
    fields:
      title:
        label: File name
        type: text
        required: true
        width: 2/3
 
      date:
        label: File date
        type: date
        required: true
        default: today
        width: 1/3

      highlight:
        label: Highlight file
        type: toggle
        text:
          - "Disabled"
          - "Enabled"
        width: 1/3

      tags:
        label: File tags
        type: tags
        accept: options
        options:
          type: query
          query: site.find("portal").tags.split
        width: 2/3

      description:
        label: Description
    type: text

  thumbnail:
    label: Thumbnail
    type: files
    uploads:
      template: media
    help: Allows for previewing the file in the highlights section. Not necessary for images.
    width: 1/2

Thank you! : )