Not quite 8" from the floor, but I had an older DMC1 that on occasion the door would do as you describe but only about 3 or 4 inches away, but the car never stopped. I fiddled with the SE micro switch and either that was it or some strange coincidence occurred as the issue hasn't been seen since.

Not the same manufacturer, but I have had others that lose their safeties momentarily, which stops the car for a second which has caused the doors to cycle because of the safety loss. Then the open limit is seen by the PDO/controller and triggers a reclose, and a restart of car motion. Not saying this is what is happening here, but food for thought. So if its happening at the same point in the shaft, it could be a trailer wire. It could also be a bouncing of a safety switch too.

I should rephrase my problem. Eight inches below the floor, the doors open, causing the car to stop.

Curious...when the car stopped below 3, did you notice if the two car call cancelled like it thought it was there? You say it stopped at two but didn't open the doors, then proceeded normally to 1 and opened. Does the problem always (reportedly) occur going down from 3? Selector Main Card or Auxiliary may be the culprit. Definitely need to chase the tool down and get your hands on a DMC Reference Guide or something comparable as there are way to many faults codes related to the Selector or CLC faults and erroneous signals. Routine the COP terminal strips and look for obvious CLC Card damage. Same in the Selector...check all molex type connectors. When you do get the tool, certainly a new hoist way scan may be in order just to eliminate that possibility.
Be sure to post when you resolve the trouble.

Almost always the safety edge cable or microswitch, rarely the photoeye cable. Remove your safety edge cable from door board and ohm it while manually moving the door to check cable and activate switch a few times, should always be below 1 ohm.

You might want to look at that DZ reed switch On the selector board. I've had that intermittently be a problem with opening the doors out of the true door zone? Worth a look. Good luck

Went back through the locks on Friday and rode the car for a few hours. Top floor lock had an unusual wear pattern on the shorting bar, the wear pattern looked like the contacts were running off of the shorting bar.

I pulled on and struck the interlock box and it was just barely loose. After re-adjusting the interlock box, I decided not to touch anything else so that I can be sure that this was the issue. I am guessing that occasionally, the lock was bouncing when the doors closed causing a re-open just after leaving the floor.

If the call comes back, I'll let you know.