Web sync deleted my empty groups and folders

I spent several hours setting up a complicated folder and group structure (About 300 folders). Luckily I backed it up. I bought Gold susbscription yesterday. All the folders were empty. I hav never backed my library to the cloud before. I initiated the syn on the phonec. All my empty groups and folders got deleted locally and nothing got uploaded.

I restored the backup and synced again. This time it synced. If I did not have the backup, I would be very desperate now.

The possible trigger might be:
1. have a completely new fresh Gold account (though I have been on Silverf or a year or so),

2. create a bunch of empty folders and groups on the phone

3. initiate a cloud sync from the phone

4. watch your folders being deleted?

attaching the folder structure in question (though I do not know if it makes a difference if the folders get created manually or are imported from backup)