Defraggler may fragment contiguous files

[thany]

I'm using Defraggler 1.08 on a 32-bit Windows 2003 server, and I've seen this weird behavior where Defraggler tends to cause contiguous files to end up fragmented. This only happens when I simply hit the Defrag button on the volume in question. This volume does have enough contiguus freespace to allow for defragmentation, altough not very much (~10% is freespace, out of 10GB total).

 

The volume has no fragmented files, and yet when I hit Defrag to sort of fill the small freespace gaps, some files get fragmented again. If I then do an analyse and defragment those fragmented files "manually", everything ends up ok.

 

How come this is happening? Any ideas?