Does your retainer fit tight against the strut tower? When I installed new front struts, I tightened the top strut nut with the weight of the front end off the wheels. When I lowered the car, the retainer moved off the top of the strut tower, allowing the strut assembly to move, clunk on tight turns etc.
I assumed the lower nut of the stut assembly was a "Nyloc"
nut like the top strut nut. When I looked at my original lower strut nut I saw it was a regular low profile nut. You can not use a Nyloc nut to fasten the upper mount to the strut. When you try to tighten the retainer it will bottom out on the taller Nyloc nut and not allow the retainer to seat tightly to the tower.