That's been mentioned before so I was looking closely at that on Friday. He took 9 threes in that game. The first three he took, and made, (first basket of the game - video below) he definitely kicked his legs out which made his form look very strange but the shot went down.
His second one missed badly but it doesn't look like he kicked his legs out.
His third three his legs went forward a little but not like the first three. He missed.
His fourth three he made when he kicked his legs out and got fouled for the 4 point play.
His fifth three he didn't kick his legs out at all and he was wide open and the shot was long off the back iron.
His sixth three he kicked his legs out and put up an airball from the right corner.
His seventh three he kicks his legs out just a little and misses long off the back iron.
His eight three he kicked his legs out a little and misses off the back iron again.
His ninth three he was wide open, didn't kick his legs out at all, and was short off the rim.
I put the time in the game for each three below if you want to check them all out.
It seems that he made some he did kick his legs out and missed many where he didn't (even a wide open one) so this small sample size might show that kicking his legs out isn't his only issue why he's missing so many of this threes. But I agree he kicks his legs out a lot. Did he do that last season?
If this is indeed the problem I would think that's an easy fix and the coaching staff probably has picked up on it and discussed it with him. Hopefully he gets out of this slump soon and goes on a heater from three.
First three (19:42 left in 1st half):
Second three (19:14 in first half)
Third three (13:02 in first half)
Fourth three (12:05 in first half)
Fifth three (9:00 in first half)
Sixth three (17:50 left in the second half)
Seventh three (17:44 in the second half)
Eighth three (8:13 in the second half)
Ninth three (6:32 in the second half)