diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 359661d4b..db6ae7b57 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -354,7 +354,7 @@ class ApplicationController < ActionController::Base
 			logger.info("--uri_exec: .....res is #{res}")
 			JSON.parse(res)
 		rescue Exception => e
-			uid_logger("--uri_exec: exception #{e.message}")
+			uid_logger_error("--uri_exec: exception #{e.message}")
 			raise Educoder::TipException.new("实训平台繁忙（繁忙等级：84）")
 		end
 	end
diff --git a/app/controllers/challenges_controller.rb b/app/controllers/challenges_controller.rb
index ebce98b62..9e87d3799 100644
--- a/app/controllers/challenges_controller.rb
+++ b/app/controllers/challenges_controller.rb
@@ -151,7 +151,7 @@ class ChallengesController < ApplicationController
   def index
     uid_logger("identifier: #{params}")
 
-    @challenges = Challenge.fields_for_list.where(shixun_id: @shixun.id)
+    @challenges = @shixun.challenges.fields_for_list
 
     @editable = @shixun.status == 0 # before_action：有判断权限，如果没发布，则肯定是管理人员
     @user = current_user
diff --git a/app/controllers/homework_commons_controller.rb b/app/controllers/homework_commons_controller.rb
index 7f2519b99..c8cf36824 100644
--- a/app/controllers/homework_commons_controller.rb
+++ b/app/controllers/homework_commons_controller.rb
@@ -1459,7 +1459,8 @@ class HomeworkCommonsController < ApplicationController
             if game_codes.count > 0
               code_rate += game_codes.map(&:rate).sum / challenge.path.split("；").length
             end
-            target = game_codes.count > 0 ? game_codes[0].target_user_id : nil
+            logger.info("#####game_codes: #{game_codes}")
+            #target = game_codes.count > 0 ? game_codes[0].target_user_id : nil
             # 作品完成时间
             game = challenge.games.find_by(user_id: @user.id)
             end_time = game.end_time
@@ -1467,7 +1468,7 @@ class HomeworkCommonsController < ApplicationController
             all_score = homework_challenge_settings.find_by(challenge_id: challenge.id).try(:score).to_f
             final_score = @student_work.work_challenge_score game, all_score
             # 抄袭用户
-            copy_user = User.find_by_id(game_codes[0].target_user_id)
+            copy_user = User.find_by_id(game_codes[0].try(:target_user_id))
             copy_end_time = copy_user.games.find_by(challenge_id: challenge.id).try(:end_time) if copy_user.present?
             # 代码部分
             code_list = []
@@ -1477,7 +1478,7 @@ class HomeworkCommonsController < ApplicationController
                 code_list << {path: path, origin_content: info.origin_content, target_content: info.target_content}
               end
             end
-
+            # TODO: 这里本来应该前端做的，但是现在页面已经刷不开了。
             {code_rate: code_rate, copy_user_id: copy_user.try(:id), end_time: end_time, final_score: final_score,
              all_score: all_score, copy_end_time: copy_end_time, copy_username: copy_user.try(:full_name),
              username: game.user.full_name, code_list: code_list, subject: challenge.subject, position: challenge.position,
diff --git a/app/models/challenge.rb b/app/models/challenge.rb
index 8e4d2ae42..adb54fae9 100644
--- a/app/models/challenge.rb
+++ b/app/models/challenge.rb
@@ -1,7 +1,6 @@
 class Challenge < ApplicationRecord
   # difficulty: 关卡难度: 1.简单 2.中等 3.困难
   # show_type: 效果展示：-1.无效果 1.图片 2.apk/exe 3.txt 4.html 5.mp3 6.mp4
-  default_scope { order("challenges.position asc") }
 
   belongs_to :shixun, :touch => true, counter_cache: true
   belongs_to :user
diff --git a/app/models/shixun.rb b/app/models/shixun.rb
index 1839edf93..81b444c0a 100644
--- a/app/models/shixun.rb
+++ b/app/models/shixun.rb
@@ -5,7 +5,7 @@ class Shixun < ApplicationRecord
   # hide_code： 隐藏代码窗口
   # code_hidden: 隐藏代码目录
   # task_pass: 跳关
-  has_many :challenges, dependent: :destroy
+  has_many :challenges, -> {order("challenges.position asc")}, dependent: :destroy
   has_many :challenge_tags, through: :challenges
 	has_many :myshixuns, :dependent => :destroy
   has_many :shixun_members, dependent: :destroy
diff --git a/public/react/src/modules/courses/exercise/new/NullEditor.js b/public/react/src/modules/courses/exercise/new/NullEditor.js
index 8cfb21a5f..9a99a067d 100644
--- a/public/react/src/modules/courses/exercise/new/NullEditor.js
+++ b/public/react/src/modules/courses/exercise/new/NullEditor.js
@@ -196,12 +196,14 @@ class NullEditor extends Component{
   }
   
   onAnswerChange = (index, itemIndex, val) => {
+    if (this.state.standard_answers[index]) {
     this.setState(
         (prevState) => ({ 
           standard_answers : update(prevState.standard_answers
             , {[index]: {$splice: [[itemIndex, 1, val]]}}),
         })
       )
+    }
   }
   addChildAnswer = (index) => {
     this.setState(