First of this is my first thread so I apologise if I have posted this in the wrong area.

Two weeks ago had my drivers side lower arm changed on my '02 ST170, last friday the arm seemed to pop out of place and my tracking went all over the place accompanied my a massive amount of vibration.

Obviously I returned to the garage where I had the work done and they replaced the part under warranty.

Last night I picked the car up and within five miles of leaving the arm popped out of place again and the vibration started again. I have called the garage and they are going to replace the part again.

I have been advised that the lower arms is a generic part that fits all Focus's of up to the 2004 models but the technical spec from ford describes its as "ST-tuned MacPherson strut, with angled coil spring over dampers and lower A-arms mounted on separate front subframe via double horizontal bushings. Anti roll bar (21 mm)"

In short am I getting the right arm fitted? or is there some specific part/bolt that is specific to the st170

Apologies for the waffling post, any help or advise will be massivly appreciated!!