How to reproduce

• Edit a content
• Insert a image (here a 532x800 pixels)
• Edit the image height (here 150pixels)
• Click on width field or press tab key

The width is not computed with the good ratio, the width remains at 800 in width field
The image is corectly resize but as soon as the focus is back to the rich text, the image returns to its initial dimension.

See on 4.1.11 and 4.2 nigthly