Best Left Forgotten

Best Left Forgotten is a main quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
After obtaining Faraday's program the player character returns to Kasumi, ending Where You Belong and starting Best Left Forgotten.

She will reveal her suspicions about DiMA and give a quest to investigate DiMa's memories, which are stored inside the Nucleus Command Center. Otherwise, the terminal controlling the locked gate to DiMA's memories will remain inaccessible until the player character progresses further in the main questline.

Once the quest has been obtained the Sole Survivor must travel into the command center in the Nucleus to access DiMA's stored memories. They must bypass radiation, protect indexers and circumvent sentry intrusion countermeasures in a virtual, maze-like environment to access to the memories.

Through unlocking the memories, the Sole Survivor also unlocks the coordinates of several locations on the Island to investigate: DiMA's secret medical facility at the Vim! Pop factory, the location of the nuclear launch key at the Harbor Grand Hotel, and the wind farm kill switch code at DiMA's cache.


 * After uncovering DiMA's secret medical facility at the Vim! Pop factory the next quest is unlocked: The Way Life Should Be.
 * Uncovering the wind farm kill switch code or the nuclear launch key unlocks Cleansing the Land.

Bugs

 * During the first memory the indexers will all cluster against the walls next to the orange memory column instead of returning to the access point, until they are destroyed.
 * FIX: Do not interrupt DiMA's voiceover while he is explaining what to do. Wait for each portion of the voice-over to finish before following the instructions he gives the player. This will prevent the glitch from triggering.
 * FIX: Place blocks where the indexers are congregating next to the orange memory column. They will pathfind correctly back to the access point.
 * FIX: Do not run the game above 60 FPS.
 * FIX: Walk or run against the indexers will prompt them to seek another path.
 * FIX: Make the bridges across the gaps wider than one block.
 * There is a bug that doesn't allow the player to start the memories. The game will freeze in the loading screen with the little loading symbol down in the corner. This can happen on any of the memories, not just one. Reloading to an earlier save might help.
 * During the first memory the small green indexers do not move to the orange memory column despite building a usable path. It may affect PS4 and even PC users as it seems to be very uncommon. This is a game-breaking glitch and one cannot proceed further in the quest.
 * There is currently a bug preventing mission completion. On one's first entry to the simulation, it may be impossible to interact with the blocks one must move to make bridges and clear the path for the beam. Exiting the simulation and restarting the console may fix this. Furthermore, turrets are not unlocked for construction when the game informs the player to construct them, making it impossible for the player's green indexers to make it to the objective. This renders the quest impossible to complete, even after several reloads and restarts. It may randomly resolve itself on the PS4 after returning to an old save. On PS4, returning to the simulation may freeze the game. There is a workaround for this bug by using the blocks to imprison the defensive robots before they enter the area, trapping them where they spawn.
 * On certain memories the indexers will not load memory past 80%. This is reported for the second and fourth memory levels. Then, when one tries to exit the memory simulation, the game can get stuck where one can save the game but cannot move around. A possible fix to this: If stuck on the fourth memory simulation, leave the keyboard/controller alone until the game recognizes the player as idle. Once it goes to the mode where the player character is looking around aimlessly, it is then possible to move around.
 * Sometimes, the orange data rings will disappear before the indexers are done with downloading the data, making the quest impossible to complete.
 * On the final memory, placing several Defense Constructs near (or within) the red barrier surrounding the data stream will cause them to fire at the dormant drones, which will then become active. If this persists for long enough, the Defense Constructs will eventually destroy the red barrier itself, bypassing the entire puzzle.