What i see is the rotation of the shoulder that initiate the turn and you lost balance af ew time at the end of your turn because of that rotation and the lining that come with.
I really can't see this as a SMIM problem, what time in the clip are you referring to?
Sure there could be more of a strong arm on the inside, but I think the feet should be worked on first.
I admit I have discounted the stopping turns, even though we all know that the last turn is the most important one.
"Someone once said to me that for us to beat the Europeans at winter sports was like Austria tackling us at Test cricket. I reckon it's an accurate judgement." Malcolm Milne