Lock this item to prevent future changes

[Efficient_Good_5784]

To clear up how the "Lock this item to prevent future changes" option works, it actually is all encompassing.

It will lock all items that have anything filled in them.
It will not lock blank/empty items.

The reason the ratings keep returning on your media is because you keep deleting them leaving them as empty entries, which the lock option doesn't cover.
If you were to leave the rating (or add your custom ratings) and leave it locked, the rating will never change until you unlock the metadata.

The same behavior happens for any part of the metadata that is left empty.
For example, if you leave the overview empty of a series and lock its whole metadata, the next time you scan over it (with a scan that will change items), the overview will be regenerated despite the metadata being locked.

Basically, the lock metadata option only applies to already-filled metadata. It doesn't apply to empty fields.

Note that there are three types of library scans:

1. Scan for new and updated files
   
2. Search for new and updated files
   
3. Replace all metadata
   

Scan for new and updated files will not regenerate metadata, so if you scan a whole library with it, your empty rating metadata will not be brought back.
If you scan with the other two, empty metadata fields will be regenerated.

Also note that using the "Scan All Libraries" button in the dashboard will not regenerate empty metadata fields in your locked items. This acts similar to "Scan for new and updated files".
However, this and any other scan type will regenerate empty fields if the library entry is either moved to another location or renamed on your server (since you changed where the database expects the entry to be).