On a newly installed nas (DS423+ in this case), there are already 36 .bak files present in /var/lib/disk-compatibilty. When run, the script doesn't make a backup of the current files because a .bak file already exists. However, this .bak file is not a backup of the current situation but way smaller.
When you restore to the previous state, the script will use the outdated .bak file so it doesn't "Undo all changes made by the script".

Steps to reproduce:

• Install a DS423+ from scratch. During the installation process it installs DSM 7.2.2-72806-3
• run: sudo -s ~/Synology_HDD_db-main/syno_hdd_db.sh
• run: sudo -s ~/Synology_HDD_db-main/syno_hdd_db.sh --restore

Expected result:

• To roll back every change made by the script

Actual result:

• Rolled back to an unknown state