I just replaced the three switches today and it is working now, yeah!
However, I tested the 3 old switches and they seemed fine. So I do not know if the switches or the connections were bad.
The two on the right side is a bit tough to do due to the tight space. And be cautious about all the wires there. Do not over stretch them. It is hard to remove the entire right side panel, so I just removed the screws out-most and in the middle, then pull the microwave out to have some room for the replacement. At this point, you can just open the microwave door and remove the two front screws which hold the switched holder in place. Once the holder is off, it is easier to work with.
For the left side, you can basically title the microwave (right side in, left side out), so that you can unscrew all to completely remove the left side panel (two screws on the back).
Sometimes you have to have one assistant. Be careful about the sharp edges. I got two cuts.
Some reference videos which show some of the intermediate steps (but no complete process available):