I am pretty new to XnViewMP so please go easy on me

I have a little problem here. When I import raw files the thumbnails look great: <fig. 1>
Now, when I change folders and come back to this folder it looks like this: <fig. 2>
When I doubleclick an item it looks like this: <fig. 3>
When I return to thumbnail explorer (which still looks like <fig. 2>, select all thumbnails en do menu / view / rebuild thumbnail it looks like this again: <fig. 4)
Moving from the current folder to any other one and back to this one resets the thumbnails again to fig. 2. These are raw files from the Sony RX10, but I've also seen it on G3x CR2 files
Am I doing this wrong?
Kind regards from Holland
Germie