Maintaining Quality of sketch image from Autodesk sketchbook to Indesign.

Hi,

I have 4 different sketchbook files that I combined in sketchbook (which I will use to re-arange the individual sketches into a better layout). I tested the export of the combined file to tranfer into Indesign. When I insert the 4 sketchbook files separately the resolution is great. However, when I insert the cobined file the quality of the image drops (even though it looks the same in sketchbook). It's not very noticible but it definately makes a difference. I attached some files showing the difference (I also tried different formats inculding bmp. psd (both from sketchbook and photoshop). Any help would be appreciated.