I'm facing this tedious issue when I replace a media item (usually an image, but I dont' exclude that it affects other media type).
Sometimes when I replace a media I have:
1) delay of replacing (1-2 hours)
2) Xibo stop working at all (the clients stop working and show the desktop)
To fix this issue I delete the assigned media from all layouts then I delete it from media library, then I re-add it from scratch.
Sometimes I notice that deleting the media from media library I can see the "previous" version listed, so I have to delete it but... I see again an older version and so on.
I have to delete almost 5-6 previous versions of the media to clean definitively it and solve the issue.
Xibo CMS 1.8.1 docker edition
Xibo clients Windows 1.8.1