I suppose it's possible that she feels limited by the leash. I know Annie liked to walk around and around in circles until just the right spot was found.
So she had trouble any time we where out running errands and she needed to potty. Also, she didn't like you watching her potty.
She was very modest in that respect.
All this to say, I don't really have any advice. But I'll bump this up so that maybe someone else will see it.