I think I got a lemon.  I had repair out six times in the first few months.  To this day it doesn't clean the silverware very well and if one plate is in ghe wrong place the top shelf doesn't get clean.  

That’s terrible.  I checked and Bosch has good reviews. Either you got a bad one or different models are better than others. Do you clean the water jets?  I read that dishwashers need to be cleaned regularly. I never knew that.  

Yes! We clean the water jets and the debris traps (there are two).  We run an empty load with Busch's recommended cleaner and procedures also.  The issue is that the spray arm doesn't reach far enough under the top shelf  to clean the entire inside of glasses or dishes on the far outside edge.  The second issue is the soap dispenser fails to open which is also related to the too short spray arm.

Is that a design problem?

I'd assume so.

I wonder if different models have different internal designs and equipment.

I would guess yes.