Best Left Forgotten

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

Detailed walkthrough
To start this mission, the Sole Survivor must first travel to Acadia and speak with Kasumi. She will reveal her suspicions about DiMA and give a quest to investigate DiMa's memories, which are stored inside the command center. Otherwise, the terminal controlling the locked gate to DiMa's memories will remained inaccessible until the player character progresses further in the main quest line.

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, robots, and then solve a series of puzzles to unlock access to the memories.

Bugs

 * There is currently a bug that doesn't let you do the memories. The game will freeze in the loading screen.
 * 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 & 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 you to construct them, making it impossible for the player's green decompilers to make it to the objective. This renders the quest impossible to complete, even after several re-loads and restarts. It may randomly fix on PS4 after returning to an old save. On PS4 returning to the simulation may freeze the game. There is a work around for this bug by using the blocks to imprison the defensive robots before they enter the area, trapping them where they spawn.
 * One can get stuck at 4th memory unlocking process where it would not go above 80% and then when one tries to exit the memory simulation, the game can get stuck where one can save the game but cant move around.
 * If you are stuck on the 4th memory simulation, leave the keyboard/controller alone until it changes as if you have left the computer. Once it goes to the mode where your character is looking around aimlessly, you can then move the character around.
 * Sometimes the orange data rings will disappear before the "bugs" are done with downloading the data. Making the quest impossible to complete.
 * On memory OJ-2NN8 the indexer bugs will not load memory past 80%.
 * 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 (note this takes a very long time).