Problem with Book 4/Chapter 3 quest

HI,

So the "Seven Gates" quest in Minath Tirith, Chapter 3 of Book 4, starts with Mithrandir handing you his pledge and telling you to speak with Thalgam, gate-keeper of the first gate, the Sword-gate. The problem is that though my map shows Thalgam standing just behind the closed gate door, to interact with him you have to go through the door - which is closed. Despite Mithrandir's pledge, I cannot open or otherwise interact with this door. The problem persists through re-logging.Am I missing something, or is this a bug?

Any help will be apprecited.

I didn't find the right solution from the Internet.

References:
https://bit.ly/2ti7tjE
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Thank you.