The mastery book quest from Hawkwind in Eondon is also part of that older quest system, despite being one of the most recent quests added, and that can interfere with that.
The old, one at a time, quests are
The old template starting quests from AoS & SE (in case someone reactivates an account closed in that era) (Necro, paladin, Samurai, ninja). These can no longer be completed.
The old escort quests (if they didn't clear once the escort timed out or you/it died - They've not been available since ML launched)
The Naturalist Quest
The Solen Matriarch
The Ambitious Solen Queen
The Griselda the Hag Quest
The Hawkwind Mastery Book quest.
Any others that I might be forgetting?