MP4 ratings are stored in the files themselves, which rules out the filesystem being an issue.
(Filesystem could still affect other file types where the rating is stored as NTFS metadata, e.g. plain text files, but if it's an MP4 file we shouldn't need to worry about that.)
Does setting the rating via the Properties dialog from Opus work or does that fail as well?
Finally i have some time to further experiment.
If i set the property over the file dialog, it sets its properly, but its not visible in Opus. I do not see any Opus specific file dialog, if it was that, what you mean.
If i just click the stars on the columns, it gets set, but then the stars are disapperaing in the view. Altough, it was set properly on the file itself (visible in Windows 10 Explorer)
So, it really does not seem to work from the external drive. I checked the same file on multiple occasions.
Network drive: working
Internal disk: working
USB Stick (Fat32): Not working
External SSD: Not working
I realize this does not answer your questions but...
I don't add ratings or IPTC metadata (Star ratings, Keywords/tags, Titles, Descriptions) to videos because I organize photo and video collections for clients, and most applications used by consumers for enjoying and managing their collection do not display that metadata, or do so inconsistently.
So, I need to rely on the filenames. I don't rate my clients videos, but if I did, I'd likely put something in the filename to represent the rating, like '5S'.
Confirmed (to my surprise). And fixed for the next update.
(Reading some other metadata was failing on ExFAT, which meant we read the rating successfully, but then failed the overall metadata retrieval and didn't actually propagate the rating through.)
I remember that i also once had ExFAT, and wasn't able to change the case for items. Sorry, but something like that is just embarrassing for some wannabe file system. Just impossible.