Now the A320 seems to dive for the first constraint, fly level until passing it, then immediately dive for the next constraint
Curious! I've never seen managed descent do anything like that, it normally hits the level restriction right at the fix with unerring accuracy. As I'm sure you know, it should start down with a V/S of 1000fpm until it meets its computed descent profile then descend with idle power until it reaches the constraint, unless you start the descent above the profile or descend with selected speed.
Even worse, if I delete all the altitude constraints, it aims to be 2000' approx 13 miles from touchdown! And then fly level until the glide.
This could be something to do with the positioning of the decelleration point in the profile. Any particular RNAV arrival into AMS, I'll have a look next time I'm there.