I know this is a year late and you may possibly not have the car anymore but I thought I'd post my experience here for anybody in the future that may have this problem and it took me a while to put my finger on it. I have a MY14 Fiesta ST which drove fine from new then on my way to work one day a van collided with the LHS on a roundabout and I caught the RF wheel on the kerb on the roundabout. So the car was repaired and all sorted and I asked for an alignment check and all came back fine, the garage adjusted the toe slightly to bring it back in line and called it done. I drove it for a while and I was convinced something was wrong but on paper all was fine. It would drive as the OP described, it would turn in one direction as it should but it just didn't feel right in the other direction. After being frustrated with it for a while I loosened both lower arm mounting bolts and tightened them back up and this solved the problem. I suspect that the impact was enough to move the lower arm on it's rear mounting as it's slotted affecting the suspension movement in ways I cannot explain haha