The Wife said, "The lights are flickering." Dimmer on aluminum wiring
The two wall-mounted lights were indeed flickering in unison. There is a Lutron "Glyder" single-pole dimmer switch (two black wires and green ground) and three cables in one normal size box. One from below, two from above. There was only a single bare aluminum wire entering the box.
None of the dimmer wires pulled free. Two black wires connected by a wire nut, not to the dimmer, were loose. It was not possible to re-cram the wiring back into the same box. The box was replaced with an Old Work Deep. I marked (taped) the wires and replaced them into the new box. In process most marks came off.
The two common black wires were connected. All white wires connected together with a dimmer wire. The remaining black wire to one dimmer wire. The dimmer ground was connected to the single bare wire. But, I extended the two bare aluminum wires to connect with the green from the dimmer. Lights do not work.
Please point to my error. And, any margin of safety that can be gained with aluminum wiring.