My front wing ones has a ripple from where it was refitted many moons ago. THey also need to be heated when they're removed - otherwise they ripple because they're removed with uneven force, which damages the plastic.

The advice I've had is that they need to be heated up, so they're a little more pliable, which will help stick them down flat - heating the door along where the moulding will go will also help a little. Obviosuly make sure it's perfectly clean along there or they'll just fall off.

I'm not sure how to cure the ripple though - I've just ignored it.