First of all - this issue seems to vary some from car to car.
On my own car (webmaster) from '98 this is not a problem.
Unfortunately the paintwork on some 156's are not the best and
it comes off even if you just rub your nail over the paint.
Check the front bumper and the bonnet for stone hits if your car
is one of these. Also check top top of the windscreen as some even
discovered rust there. Contact your local dealer to see if they can
take this under warranty. Some does and some doesn't... But if you
can show the dealer that they can rub the paint of with their nail,
it should be easy to convince them I guess.