How to replicate:
Create this structure.
Folder1
--- Folder 2
--------Site
Right click on Site --> Move To --> Folder1
Tree collapse. Bookmark is being transferred to correct path.
If Folder2 has only one bookmark, that was moved, is being deleted.
The same behavior can be replicated if you create an empty group, close site manager and then start it again. Folder vanish!
Is this normal?!