Steps to reproduce:

Start from an eZ Publish 5.3 or 5.3.1 environment.

1. Log in to the administration backend
2. Create a new article in any location you wish
3. Add an image to the "image" attribute field
4. Publish your article
5. Edit your article again
6. On the image you just added, click on the "Remove image" button

Check your image attribute. The image looks like it hasn't been removed, since we still can see it it the page.
But in fact the image has been removed. Only the information on the page hasn't been updated.

If you re-publish your article or save the draft, causing the page to reload, the related image will disappear as expected.