When I try to change Thumbnail size it works to about 150-200 pixel, after that the box will get bigger and not the Thumbnail itself... refreshing does not change anything... even if i move to new fresh folder the Thumbnails stay tiny small

It seems XnView do not scale ALL thrumbnails proper may? Some are big some stay small

HMMM already found the solution/OPTION: Create thumbnail from orginal image if embedded is smaller....