If you are riding in the Crow's Nest when a Ship reaches a port, the Disembark button appears as normal. However, once you climb down from the crows nest to the deck, the button disappears and you have to get really close to the Wharf manager to get it to reappear.

I think what is happening is that once you climb down from the nest, the distance check to see if the button should appear is reverted to the old short distance.