Backup copies useless when saving as hierarchical folder structure

[Lavooo]

Version, Operating system
Version: 1.6.3
Operating system: Windows 10

Describe the bug
I am saving my notes as "Multiple Files in Hierarchical Folder Structure".
I am creating 1 backup copy while saving.
The backup copy was created, but most of created folders are empty.
If I try to open this backup copy I get an empty document.

To Reproduce
Steps to reproduce the behavior:

1. Disable autosaving (probably not important)
2. Create some notes with multiple nodes and with at least 2 levels of depth.
3. Save your notes as "Multiple Files in Hierarchical Folder Structure".
4. Go to Preferences/Miscellaneous and check "Create a Backup Copy Before Saving"
5. Set "Number of Backups to Keep" to 1.
6. Save your notes as "Multiple Files in Hierarchical Folder Structure".
7. Check structure of Backup Copy folder
8. Try to open notes from Backup Copy Folder

Screenshots
Not applicable.