F-Body Europe

I just got an alignment done today, the car felt very nice, stable and way less nervous afterswards... so, great.
But as soon as i drove home into our driveway and the left front tire hit the curb, i heard that -well known- "klonk"... and the left side camber went again all the way to the maximum and the steering wheel isn´t really straight anymore when i drive straight.
The last alignment lasted something like 6 months before exactely the same happened... well, at least better than 2 hours.

So, my question for the suspension gurus is:
What can i do to prevent this?
More torque on the retaining nut?
Welding the nut in place? (Ok, sound ghetto...)
...?

Buying a Porsche is not an option btw.

First
Physically check that the Camber nut and bolt moved. If it did take it back and tell the shop to do it again. This time ensure they torque the caster and camber bolt.
If the bolt is not sliding check the camber and caster bushing for serviceability.