importing collapses collection tree

szallomany

If I export a collection with more than on elevel of subcollections than upon importing it back (i just tested functions and how can I move zotero files) i found that the collection tree structure collapses. I only got in the "Imported on..." folder my first level folders and then all of the lower level folders dumped into it.
I have the newest zotero and ff at the moment