All,
I was able to fix my 15C LE (#02198) with the bad divide key. Turns out it did not have any bits of white plastic under the dome. Instead, the dome was not aligned properly on the "sticky" sheet of plastic that holds it over the target PCB traces.
I cleaned the dome and the PCB traces anyway, then carefully centered the dome on the PCB traces and stuck the sheet down on it (it took a couple tries to get it just right) and now it works fine.
I had trouble getting the feet off without messing up the adhesive, so I bought some new feet on TAS. It turns out the feet on the original Voyagers are about 1 mm thick, but the feet on the 15C LE are thicker and sit in a well. The replacement feet didn't stick out of the well to contact the surface when I sat the calculator on a table. Simple solution: I bought more than enough feet, so I stuck two replacement feet in each well. Now the feet are a tad taller than the original feet (which are probably more like 1.5 mm) but perfectly acceptable for my use. The foot wells still hold them in place when I slide the calculator in and out of the case.
I sent a couple of the feet I took off to the seller so he/she can get exact measurements.
Thanks to the forum members for posting instructions on disassembly/reassembly and to the TAS seller for working with me.
Dale