Best posts made by dacia_and_gauls
Running ahead of them and entering the training area before they got there worked for me AND|OR reloading a save before entering the hall.
Balin(?) needs to enter and follow you around to give instructions. If he doesnt, then he is stuck on his friend, and doesnt complete the walkthrough.
If they are stuck on each other and not following you around, perhaps even try walking into them to seperate them, then continue training of -->Dummy on right-->Tough dummy-->Ledge dummy-->Air drop dummy-->Haystack dummy.
Also make sure to talk to everyone in the hall to avoid the bug where you go to the docks after hidden blade training and the dialogue doesnt continue as well.