backend/src/main/java/core/entities/timemanager/Task.java

@@ -75,6 +75,8 @@ public class Task {
            clonedSchedules.add(clonedSchedule);
            clonedTask.getBasicTaskSchedules().clear();
            clonedTask.getBasicTaskSchedules().add(clonedSchedule);
+
+           clonedSchedule.setTask(clonedTask);
        }
 
        Set<Task> clonedSubtasks = new HashSet<>();