Your server is returning invalid data and makes Symfonium stuck in a loop, so the sync actually does not finish in the last logs.
2024-10-25 20:57:18.935 Verbose PlexLogger <-- [675] 200 OK http://192.168.178.37:32400/library/sections/8/all?X-Plex-Container-Start=373016&X-Plex-Container-Size=1000&type=10 (6ms, unknown-length body)
2024-10-25 20:57:18.936 Verbose PlexLogger <-- [675] {"MediaContainer":{"size":0,"totalSize":373023,"offset":373016,"allowSync":true,"art":"/:/resources/artist-fanart.jpg","content":"secondary","identifier":"com.plexapp.plugins.library","librarySectionID":8,"librarySectionTitle":"Music","librarySectionUUID":"adfb3d8a-707c-49d4-abb6-574f2a64a9e7","mediaTagPrefix":"/system/bundle/media/flags/","mediaTagVersion":1728413652,"nocache":true,"thumb":"/:/resources/artist.png","title1":"Music","title2":"All Artists","viewGroup":"artist"}}
I request songs starting from a position, the server returns no song but tells me there’s still 7 songs missing (total 373023 but 0 result when asking starting 373016)
A case I never saw nor think should be possible, so Symfonium just keep asking give me those damn 7 songs and the server keeps answering here’s 0 songs, ask again for the 7 missing 
I’ll add a security around this case, but there’s something strange on Plex side.