KB: Image description in articles are de-associated from image

KB: Image description in articles are de-associated from image

When we add images into article of the knowledge base, we add description to them, which are displayed as a legend below the image. 

Image with legend after its creation:


But when we edit again the article, the description is no longer associated to the image (description field is empty) but is only visible as a text, but the layout is broken : this legeng appears next to the image and not below it.

Image + legend after edition:

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=> How can we fix that