The CU survery is done on percentages of all dishwashers. So, your model (which is a bit unique) may or not be bringing the average down. It's also done on dishwashers that are five years or less.
I can't say that I have heard of this issue in this particular model before. I can say that any number of things could cause this buzzing noise.
Try giving the arms a spin one at a time to see if something is causing the arms to make this noise. Check to see if one might be very loose.
Try listening carefully to see if you can pin point where this noise is coming from. Is it coming from the control board? A loose connection (or any number of parts there) might be reacting to a stronger cycle.
A service call should solve your problem for less than the $200.00 that you stated above. I say this because it appears to be running correctly (from everything you have stated) except for this noise.
Can you pinpoint the problem to the motor? Then, a loose motor mount or anything else you see there that is not firmly attached to the chassis could be the cause.
Is everything secure there and it seems to be the motor itself? Then, this repair will likely be more than $200.00.
Let me know if I can help with anything else.