[
  {
    $project: {
      _id: 1,
      followUps: 1,
      duplicateNames: {
        $filter: {
          input: {
            $map: {
              input: "$followUps",
              as: "f",
              in: "$$f.name"
            }
          },
          as: "name",
          cond: {
            $and: [
              { $ne: ["$$name", "Check_in"] }, 
              {
                $gt: [
                  { $size: {
                      $filter: {
                        input: {
                          $filter: {
                            input: "$followUps",
                            as: "innerF",
                            cond: { $eq: ["$$innerF.name", "$$name"] }
                          }
                        },
                        as: "duplicate",
                        cond: { $eq: ["$$duplicate.name", "$$name"] }
                      }
                    }
                  },
                  1
                ]
              }
            ]
          }
        }
      }
    }
  },
  {
    $match: {
      $expr: { $gt: [{ $size: "$duplicateNames" }, 0] }
    }
  },
  {
    $project: {
      _id: 1
    }
  }
]