Shipbreaker (quest)

Shipbreaker is a side quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
While exploring Far Harbor, you may randomly pick up the Shipbreaker's radio frequency, immediately starting the quest. Follow the signal to a patch of land near a ruined house, where you will find Shipbreaker, a unique fog crawler. Once the fight is over, you are prompted to speak to Old Longfellow. He will talk about how he has been searching for Shipbreaker for years. Tell him that Shipbreaker is dead, and the quest will complete with you earning Skipper's Last Stand, a unique harpoon gun that Old Longfellow was saving to deal the final blow on Shipbreaker with.

Bugs
If a player doesn't track it down during its original appearance it may vanish with the message "the shipbreaker has moved on for now". It will then fail to reappear and its radio signal will be blacked out even though it will still lead you to the quest location.
 * This can be fixed using the console commands on PC. After travelling to where the Shipbreaker should be type in to get the shipbreakers ID. Then  whatever the id is. Once this is done it should be showing at the top of the console. Then type, press enter then  and press enter again. Once the console is closed, the shipbreaker should spawn and you can kill it and finish the quest.
 * The game will sometimes bug and the radio signal will disappear permanently, if this happens you can use the following console commands to find and reveal shipbreaker:, , , where xx is you load order number (normally 03).

The location can still be tracked from the radio menu even though it is blacked out. Scrolling down to the location of the radio frequency, will still lead to a location regardless of the quest monster being there or not.