Since I picked up 10515, the door ajar light has been on. Which is also how I killed the battery.
The door ajar light illuminates based on one of the door switches (two switches on the driver’s side and one on the passenger side.) On the driver’s side, the top switch controls the key buzzer – if the door is open and the key is in the ignition, the buzzer will sound. I’m not sure if DMC CA pulled the wires or if the first owner did, but the buzzer doesn’t sound.
The bottom switch is what controls the door ajar light – and the three door marker lights – and as explained by Danny at DMC, sometimes, after years of the door being closed and the switch being pushed on by the door, it gets pushed into the sidewall, which means that the switch is no longer depressed far enough to open the circuit. Which means, that the door ajar light stays on – as do the door marker lights. And that’s how I killed the battery – by parking the 
car and not noticing that the door marker lights were still on, even though the door was closed.
So I finally crawled under the dashboard and studied what was going on. Since the top switch was already unplugged to stop the buzzer, and doesn’t seem to be as pushed-in as the bottom switch, I moved the connections to the top switch. And voila – the door ajar, and the door marker lights, now turn off when the door is closed! What a great, simple fix.