Very difficult to drop images on materials in scene graph

This is broken out from QT3DS-2548.

I am dragging images (.png) from the project palette to a material in the scene graph (to apply it as a texture map) and am experiencing below issue.

I have used the basic cube object and dropped both on the material as well as on bump and diffuse maps.

Issues

1. Dragging to a material or texture map in scene graph.
   1. The yellow marker often gets stuck on the first item I drag it over and it is really difficult to get the yellow marker to the object that mouse pointer is on.
      
   2. When I drop it, sometimes (very often) nothing happens.