K1 predictions — written before the detach (2026-10-14 ~23:00 CEST)

With Media B detached (the guest keeps a dead mount; reads give I/O errors — S5):

a. Plex scan with autoEmptyTrash OFF: B's items stay, their parts unavailable. With it ON (the default): the scan REMOVES the B shows/films (American Horror Story, Matchbox, Who) and the B half of Slow Horses — or, because the folder answers I/O errors rather than „empty", Plex may refuse to treat it as gone and keep everything. Jellyfin scan: removes B's items. After re-attach + restart + rescan: items come back as NEW entries; Plex's watch count on the probe episode is lost unless Plex matches it again by GUID (Plex keeps view state per GUID — it may survive).
b. Sonarr/Radarr refresh+rescan: the B root folder is inaccessible; Sonarr's own failsafe („root folder is empty — rescan will not update") keeps the files' records; nothing is unmonitored (the option is off). With the option ON: still nothing, if the failsafe holds.
c. After re-attach + stop/start: qBittorrent and Transmission recheck or show „missing files" for B's torrents for a moment, then continue without re-downloading.