Time: Various
Frequency: Always
World name: Midgardsormr
Character name: Randolont Althoreaux
NPC name: Milkmist Makers
Monster name: N/A
Class/Level: 50DRG
Party or solo: solo
In-game time: Various
Area and coordinates: various
Steps:
1. Accepted quest from Moxia
2. Talked to Mysterious Sylph and got invisibility
3. Attempted to interact with Milkmist Maker and was unable
4. Invisibility ran out and attempted to interact with Milkmist Maker again. Succeeded despite NO invisibility.
5. Continued to second Milkmist Maker without reapplying invisibility and succeeded in completing the quest.

This quest is clearly bugged as you cannot complete it while invisible (the intent) and CAN complete it while visible.