Here's part two.
After I tested the grid, it was time to remove it from the shoe. It's held on with 2 screws. The reassembly photos show them later as I tore into the project without photographing disassembly.
I then had to disassemble the handle. It takes a special torx bit with a hole in the end. I happened to have it in a bit set I got from Northern Tool. I then desoldered the two main head wires on the circuit board.
Once the shoe is free, I ground off the rivet heads slowly and carefully. Don't pry the element cards apart. They'll break. Once I ground the four rivet heads off, I got the cards apart. Remember how they go together. Photograph your steps.
You'll see the knife pointing out the rivet size. The screw next to it is not correct. Don't use 4-40. Use the stainless 2-56 as shown, the shortest length you can get, otherwise you'll be cutting them.
I found the nichrome wire burnt through right where they looped it round and round the end of the card where the rivet goes. I just unwrapped one span and wrapped it around the screw. I cut off the excess. I wrapped the resistance wire around the bottom one too to get a good contact.
I put the top card back on and add the wires. The lengths are different so I made sure to reinstall them in the right place. I tightened them down carefully as not to crush the cards and break them.
I then put the element assembly back in the shoe. The nut would not let the fixture plate bolt back down. I drilled a clearance hole for it.
I snaked the wires back through the handle and resoldered them to the board in the right arrangement. I then screwed everything back together.
I plugged it in as it rested on a glass surface. Wisps of smoke came out, but then went away. I think it was probably machine oil from the new stainless screws, or my hand oils on the card.
I unplugged it and took the shoe off after it cooled to see if there was anything melting. Nothing melted. So I plugged it back in after bolting it back up.
I set the iron to 100°C and the light went on and after a few seconds it began to blink line it should.
I verified the temperature with my old pocket thermometer. Since that old tool has not been set to ambient temperature, I trust the Coverite Iron to be working at the temperature set on the dial.
So the fault lies with the nichrome wire quality in my iron. The fix was lucky in that it was not in the middle of the heat grid. I bought a Top-Flight on craigslist just in case this one fails again.
The screws to fix it cost under $2. The iron hopefully will last. The grid is serviceable if I ever need to replace the wire element.
