I get told, ride the gait first before riding the movement. Make sure you have a good working gait first before asking for lateral movement. I also find that if I draw my leg back more (the one asking for the haunches to step over) and bump in time with the horse taking a step with that hind leg, they understand it better. As they get it better, you don't have to be so obvious in asking.
Make sure to use clear half halts so the horse understands that it can't just blow forward through the leg yield. I would also err on the side of riding them straighter, as it is easier to add flexion later than to fix a big shoulder bulge with trailing haunches.
Thank you for replies, there are several ideas here I can take to the arena and practice.
oops didn't hit send, now I can report we have a much improved leg yield, can't say for sure what did it tho.
I reviewed aids, did several stretchy circles, gently applied aids being very conscious of where my seat/legs/hand/s were and voila, a much nicer leg yield.
thank you for all ideas!