I was taught this in the air force years ago - clean towel, parts laid out in the order they came off.

Checked everything. My son came into the shop and asked what was up. He took a second look at everything and found a barley visible hairline crack on the stem. The crack was running up from the bottom pinch bolt of a Ritchey WCS stem, and yes, I torque to specs, 5nm in this case with the Ritchey torque tool. Checked it with my Park torque and the wrenches agree, so a bum stem or just wear-and-tear I guess.