[gumba]

If you change the front settings the rear is affected. If he didn't check/adjust all 4 corners then it wasn't done right. If you have more front camber on one side than the other it will pull to that side.
For a n.a. street car I like -1 -1.5 front and -1.5-2.0 rear camber, 1/16-1/8 toe out front and 0 toe rear.

It could be a sticking caliper like mentioned above. Is it pulling the first time you brake? Could be sticking when it gets hot which might explain why it seems random.

I would find a Porsche shop that can do 4 wheel alignment & corner balance. Also have them check the suspension components for wear.