It appears this has been fixed w/ the current PMS beta (version 1.24.0.4897):
From Plex Media Server - #453 by drzoidberg33
Plex Media Server 1.24.0.4897 is now available to Plex Pass users in the Beta update channel.FIXES:
- (Collections) Missing hubs when an item is part of a manually ordered collection (#12862)
