This may have been posted already but I have not seen a fix in the latest patch.

The issue is, if the player sides with the Institute at a certain point in the game (I believe it's the Mass Fusion quest), this triggers a bug where the Railroad headquarters cannot be entered during the End of the Line quest. When you get to the dial that opens their secret entrance, the the dial will turn but you cannot interact with the center button, making it impossible to enter the "RAILROAD" code and get into the headquarters, thus rendering it impossible to finish the quest and complete the main storyline.

Some have been successful with a barrier-breaking glitch that will "warp" you into the adjacent room or area if you exit your power armor at precisely the right time next to a wall, but this does not work across all platforms and is in fact a glitch in itself.

Yes there is a lot to do in Fallout but for those that want to finish out the main story this is indeed game-breaking. Please patch this soon for us loyal players.

Thanks.