When selecting the gate times, the 1.0 s button didn't seem to be operating. Upon further examination, when pushed hard, it did finally go to a 1.0 s gate. Obvious issue - a cleaning was needed. Since the entire panel will be exposed, they will all be cleaned, I was thinking. But it wasn't to be.
The button assembly isn't meant to come apart. They decided that it would never need to, and so used metal clips that do not come off (without breaking pins). After considering all the options, and test-prying the back, I determined a way to at least clean the stubborn button.
I used a material that was part of a new clean absorbent pad meant to soak up spilled oil. Seems like an odd choice, but it had a texture that I thought would clean the carbon pad and still be able to get into the very thin opening. Once I pried up the back plastic as far as I dared, I stuck in the material. Each time I pulled it out I pressed the button down against it. I did this about 6 times and put the board back to check the button sensitivity. After a few more cleanings, the button had returned to normal. Since the back was pried up, I cleaned a few more buttons around the area the same way.
Whew!