Images not rendered in preview starting from Decap CMS v3.13.0

[lbalc-dennemeyer]

Description
After upgrading Decap CMS from version 3.12.2 to 3.13.0 and later, images are no longer rendered in the admin preview pane, although they are still correctly displayed in the editor and in the deployed (live) site.
From the admin interface:

The image block shows correctly in the editor, including the thumbnail preview and controls.
However, in the preview panel, the image is missing and only the surrounding text content is rendered.

Importantly, this issue is limited to the admin UI preview:

• Images display correctly in the deployed site
• Images are stored and referenced correctly
• Images are not rendered in the CMS preview pane

This indicates a regression specifically affecting the preview rendering layer, rather than image upload, storage, or content generation.
The behavior works as expected in version 3.12.2, confirming the issue was introduced starting with 3.13.0.

To Reproduce

1. Go to CMS
2. Open any page with images
3. See that in preview they are not visible

Expected behavior
Images are visible in CMS preview

Screenshots

Applicable Versions:

• Decap CMS version: 3.13.0+ (issue), 3.12.2 (last working)
• Git provider: Azure DevOps
• OS: Windows 11
• Browser version: Edge Version 149.0.4022.80 (Official build) (64-bit)
• Node.JS version: v25.9.0

CMS configuration

  backend:
  name: azure
  repo: 
  tenant_id: 
  app_id: 
  branch: main
  
media_folder: src/static/img
public_folder: ../static/img

collections:
  - label: 'Title'
    name: 'Title'
    folder: 'src/docs'
    create: true
    slug: '{{slug}}'
    extension: 'md'
    format: 'frontmatter'
    fields:
      - { label: 'Title', name: 'title', widget: 'string' }
      - { label: 'Position', name: 'sidebar_position', widget: 'string' }
      - { label: 'Body', name: 'body', widget: 'markdown' }
    sortable_fields: ['sidebar_position', 'title']