I've also had major problems with 'Shop', it's fucking stupid IMO.
With the turning, are you supposed to do it once? or non stop until it changes? Also, is there a specific direction you need to start on?
(I noticed in lock picking, if you do it really slowly, and STOP rotating as soon as the arrow changes, it picks the lock much faster... previously i had been just rotating as fast as I could, which was usually met with strange looks by those in the room I was playing in)