调整

app/jobs/create_subject_course_student_job.rb

@@ -10,7 +10,7 @@ class CreateSubjectCourseStudentJob < ApplicationJob
 
     CourseMember.bulk_insert(*attrs) do |worker|
       course.subject.subject_appointments.each do |app|
-        next if course.students.where(user_id: user_id).any?
+        next if course.students.where(user_id: app.user_id).any?
         worker.add same_attrs.merge(user_id: app.user_id)
       end
     end