Given some of the recent issues related to posters / artwork missing, it could be a useful feature to be able to wholesale re-fetch all metadata from the source for all existing library matches. In other words, do not disassociate the content matches, but instead preserve the matched content associations and instead just re-fetch the latest metadata for every match. While this feature request is in reaction to the issue mentioned, I think it could still be a useful feature outside of this context.
Presently I’m going through all the items in my Movies library that are missing a poster and manually editing then re-selecting the matched title so that the poster artwork gets fetched from the source. It’s going to be a slow process, probably spanning a few minutes each day over a week or so–as this is not a tremendously urgent task and just gets done in various moments of downtime–to get all the posters back, as I don’t want to clear all metadata and thus lose the manual matches.
Having said that, I think the feature should behave as though someone manually selected the “Edit Metadata” option for a title and simply re-selected the match, except do this process automatically for everything.
Perhaps I’m just speaking for myself, but I could see people wanting to regularly re-fetch metadata from the source at least a few times a year, given how metadata and posters are always updated on these services. I would use it to keep the library feeling fresh, but also to solve the current problem.
I think there’s an argument to be made for its separate but complimentary existence, distinct from having to clear all metadata and starting from scratch. I generally steer away from a knobs-and-dials approach to user settings and preferences, which is just one reason why I prefer iOS to alternative OSes, so I think this is not quite in that territory of excessiveness.