FM changes image attributes from width/height to scale

This question concerns FM2015 / DITA 1.2

When I in insert an image then FM automatically inserts appropriate width/height attributes according to the dpi that I select. However, when I change the image size after that by clicking and dragging a corner (as you usually do), then FM removes the width/height attributes and instead inserts a scale attribute.

Is there a way to avoid this? We need width/height attributes.

I am not sure if I need to look into the r/w rules, because as long as I don't touch the image the width/height attributes remain. it is only during manual changing of the image size that FM removes them.

Robert