修复

app/controllers/api/v1/issues/milestones_controller.rb

@@ -11,7 +11,7 @@ class Api::V1::Issues::MilestonesController < Api::V1::BaseController
     @closed_milestone_count = @milestones.closed.size 
     @opening_milestone_count = @milestones.opening.size
     @milestones = params[:category] == "closed" ? @milestones.closed : @milestones.opening
-    @milestones = milestones.order("#{sort_by} #{sort_direction}")
+    @milestones = @milestones.order("#{sort_by} #{sort_direction}")
     if params[:only_name]
       @milestones = @milestones.select(:id, :name)
       @milestones = kaminary_select_paginate(@milestones)