So... this is a really odd set of circumstances, but is technically a possible bug that people could encounter.
When you are in the end game sequence, you can opt to visit your haven between missions (mine was Skyline). Now when you open the doors or either of the grates, you go back to the end game sequence. However, if one of the grates is already open, you can exit down the ladder to the downtown hub as normal. If you talk to the cabbie, Griffith Park appears as a destination and if you go there, you are stuck as Jack will not speak to you. If you walk into the Ventrue Towers, that sequence begins as normal.