Plex not scanning several directories since 1.16 version (Synology server)

[nibbles]

Hey now, there’s this probably important,

Plex Media Server security changes for Synology users

Community Announcement - Synology users - Security update. Server Version#: Plex Media Server 1.15.4.994 and above By popular customer request and to improve the safety of your media, we’ve made a small but visible change to what PMS can do on your NAS by itself. We have removed user plex from the administrators group. This was a holdover from DSM 5.2 when it was required for PMS to run properly on the NAS. Now, with DSM 6 and above, this is no longer required. By doing so we’ve lower…

and in general all good things are here
https://forums.plex.tv/t/synology-faqs-read-this-first/274891