Re: a teaching mistake
I think you should have stopped doing the technique.
You probably choose one of the best uke that were available.
And even one of the best did not know how to act as uke.
Now, if you would have taken another uke that could take what was coming, changes were that noone would be able to perform the technique.
Because there are no ukes that know how to handle it.
I believe you should first have taught the uke way of the technique.
And when you see that everyone is getting familiar with what needs to be done, then you can try to do the technique again.
And better find a way to learn the ukemi without the need to go back to the technique.
Hope this rambling made some sense.
In short: if something is not working, analyze the different parts peise by peise, then put everything back together.
My 0.02 euro.