Defraggler happily tries to defrag files that have a single fragment. This behavior makes file by file dragging difficult as you need to uncheck previously defragged files before defragging new ones.
After defragging the ones with a single fragment should be unchecked and grayed. Just before a new defrag these grayed & defragged ones could be moved to the bottom of the file list where they belong.
I like the mode btw where you can select what to defrag, very powerfull on small disks (so please keep in in the application)!!!