Approaching junctions to turn left: Signal issues

Not using MSM routine

If this persists after you have mentioned it there are a couple of prime causes.

One: The reasons for using the MSM routine are not fully understood or...

Two: You are being retrospective with any instruction that you offer (or failing to instruct or prompt with questions where required).

After spotting an error and checking for understanding, you might need to give positive instruction - even with the appropriate knowledge in place. Discuss the fix with the learner, ask how they feel that you can best help them to sort out the issue. As always, if giving full instruction do not carry on for too long - otherwise the learner will start to become dependant on your prompts.

Signal timing: late/early/omitted

If this is a persistent problem the reasons are the same as those given above for the MSM routine...

Watch out for parked vehicles immediately before left turns - these can result in a left signal (for the turn) followed by a move to the right to pass the vehicle.

Next: Step 6 - Issues when approaching to turn left - Speed