I can't enter the Forbidden Halls (The Purloined Letters quest)

[Jonny Friggin Panic]

I've started this and told Phasmer I was ready, now my task step is to Enter the Vaults, but the circular grate marked on the map just... doesn't do anything. No prompt at all. What am I missing.
(I see there's a bug if you take a ladder out, you can't get back, but I haven't been in there at ALL. Just so that's clear.)

[Nemesys9999]

After talking to Grim in the Serpent's Cave, join Phasmer in Alessa's Livrarium. Talk to him, then enter the vault through the manhole just behind him. Steal the key to the safe from a Key Master or sentry.

[TΞSTOSTΞROWNLOL]

Op, you do realise that your title is kinda asking for it right :P

[Jonny Friggin Panic]

Originally posted by TΞSTOSTΞROWNLOL:

Op, you do realise that your title is kinda asking for it right :P

Why be rude and actively useless when you could be quiet and passively useless? Do you need the attention?

[Skellymax]

Yup. Same problem. I talked with Phasmer, the quest giver standing in front of the grate, then I left. When I returned I was unable to interact with the grate and Phasmer was gone. I suspect the trigger to make the grate interactable requires speaking with Phasmer, but after that first time he's probably already inside the grate. Faction softlocked. O___O