Sleek-looking but functions poorly

Bought this Sharp R-426Hs 1200-Watt 1-3/5 cubic foot, modern countertop oven for $195.73 eight months ago. Loved the sleek, stainless steel look and after getting used to the buttons on the inside of the door I really found that design potentially superior to the typical button-cluttered microwaves.

I never found a need for the sensor buttons nor many of the other buttons provided, like the one for "hot water".

Two serious problems: (1)Using vented cookware such as a microwave popcorn popper and a Tupperware steamer in the microwave has discolored the white interior terribly. The entire ceiling of the thing is now a dirty-looking yellow/brown.

I am 60 y.o. single woman and I clean all my appliances after each use. This microwave CANNOT be cleaned inside by any of the recommended methods. Furthermore I use it lightly, for coffee, TV dinners, steamed vegetables, rice, water and popcorn!

(2) From the first use, the ON and OFF buttons would not work properly. I thought they might loosen up with use. No. One must push the OFF button repeatedly to turn oven off and sometimes the button gets stuck sideways and the only way to stop the cooking is to open the door while oven continues to cook. So although I love the sleek, stainless exterior I'd rather be able to clean it properly and turn the oven off and on as designed.

A third minor problem: the blue saran-type wrap covering the outside of the oven for transport does not come all the way off. Edges stick between the outer and inner layers of the oven. After most of the paper is removed, a tiny paper ruffle remains around the edges that tweezers can't even pull off. Its not a big deal but to a neatnick it is unattractive and annoying.