Trouble Brewin'

Trouble Brewin' is a side quest in Fallout 4.

Detailed walkthrough
You get the quest from Rufus Rubins in the Hotel Rexford, located in Goodneighbor. Your task is to get Drinking Buddy, a Protectron modified to function as a microbrewing machine, from The Shamrock Taphouse and bring it back so no one has to keep drinking the barman's normal swill.

When you reach The Shamrock Taphouse, there will be a few easy raiders inside, and an elite raider named Gaff located upstairs, as well as several mole rats down in the basement where the robot brewing machine is found. When you enter the pub, the room upstairs on the door to the left is a room with a safe. Down in the basement, Buddy can be found inside a Protectron storage container, locked with an expert level security terminal. There is a note on Patrick's Terminal that says he's stashed the password down in the basement. The password is on top of the shelves underneath a flashing red light - to reach it, you must jump onto the shelves from the stairs leading down into the basement.

The note located on Patrick's Terminal in the basement indicate that the robot may be a bit frail, and expresses concerns about transporting him to the buyer. There is no need to be concerned - send Drinking Buddy to the Hotel Rexford. You can fast travel to Goodneighbor (Buddy is not essential and can die if not escorted, which results in him not appearing at destination so save and either travel with him or set him as essential; read the notes section for more details). If you do fast-travel, when you arrive you should sit and wait for a few hours. Buddy will either arrive in Goodneighbor or will be in the Rexford Hotel.

Occasionally, his Protectron programming may cause him to deviate to chase an enemy. Once the enemy has been lost or killed, he will return to his journey to the Hotel Rexford. You will not receive an updated quest marker until you arrive back in Goodneighbor.

Once installed at the Hotel, you can ask Buddy to tell you a joke, receive a daily batch of beer from him, ask him where to find additional recipes or store any Gwinett or Nuka beverage in him, which will turn ice cold after 12-24 in-game hours. Additional recipes are located on holotapes found in local bars and breweries around the Commonwealth, one of which can be found under a counter in The Shamrock Taphouse.

Alternatively, Buddy can be sent to a settlement of your choice, which will enable faster access to his services. You will be able to send Buddy to Hotel Rexford at any time after that, but the quest will not be considered complete until you do so and sell him to Rufus.

Bugs
Even though Buddy's home destination is Hotel Rexford, he will then head back to The Shamrock Taphouse. If the player returns to Hotel Rexford and uses to get Buddy back to the Hotel Rexford, Buddy will still return to the Taphouse afterwards.
 * If player decides to send Buddy to Hotel Rexford, and Buddy makes it to Goodneighbor by himself without being escorted, he will be waiting outside the Hotel Rexford. After the player talks to Rufus, the quest hangs at "Bring Drinkin' Buddy inside the Hotel Rexford". Talking to Buddy will not get him to enter or follow you into Hotel Rexford, and he stays in his "Introduction" loop; he cannot be exchanged with or given more recipes, even if the player has read the recipes in their Pip-Boy.
 * The quest can be completed by using the console, and entering . This gives you the reward Rufus promised you and completes the quest, removing it from the log.
 * If Buddy still provides the dialogue choice to be sold to Rufus after the quest completes you can change this with the command . The dialogue choice will permanently change to "No thanks" and helps prevent the player from accidentally re-assigning Buddy.
 * If the player decided to keep Buddy when first encountered without the quest and sent him to a settlement the quest may become broken and can't be completed as buddy will set the home parameter back to Taphouse and will not move to Hotel Rexford.
 * To avoid this, the player (if without the quest from Rufus) must not send him to a settlement if decided to keep him as of this moment the home parameter is still set to The Taphouse. Get the quest from Rufus, then tell Buddy to move to Hotel Rexford, at this stage the home parameter will be set to Hotel Rexford. The player is then required to escort Buddy to the hotel, after which the quest should complete properly.
 * On PC this bug can be fixed with the use of console commands. One can reset the quest with the command . After that, it is advised to follow the steps detailed above to avoid any further issues.
 * If player decided to keep Buddy after telling Rufus he would send him to the Hotel Rexford, one optional objective completes, but the quest remains in the log stuck on (Optional) Send the Drinkin' Buddy to the Hotel Rexford.
 * To keep Buddy and to complete the quest using the console, enter . This gives you the reward Rufus promised you and completes the quest, removing it from the log. Buddy then remains in the player's possession.

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