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

@@ -73,6 +73,8 @@ public class Task {
        for(AbstractSchedule abstractSchedule : this.basicTaskSchedules) {
            AbstractSchedule clonedSchedule = abstractSchedule.cloneSchedule();
            clonedSchedules.add(clonedSchedule);
+           clonedTask.getBasicTaskSchedules().clear();
+           clonedTask.getBasicTaskSchedules().add(clonedSchedule);
        }
 
        Set<Task> clonedSubtasks = new HashSet<>();