This oven/micro would rate 5 stars if the micro had a buzzer you could hear.  I assume the engineers are working on a fix for this problem.  It does have a pathetic little squeak you CAN hear if your ear is against the unit.  Otherwise, you have to buy a kitchen timer to accomplish what those very well-paid engineers should have thought of in the first place.  Please let me know when the replacement buzzer becomes available.  Thank you.  
P.S.  They might think about using the same buzzer that is on the lower unit.  It’s LOUD.  Just a thought. . . . . .