Next day update:
Stitch is still doing his #2 outside the box. Popped a squat right in front of the wife, luckily she moved him to a towel before he pinched it off so it was easy to dispose of, but the smell was still horrendous
We've got 3 litter boxes through the condo. The biggest concern is this has been
on-going for 2 months,
before the move. No word back from the vet as their lab takes 24-48 hours. We're really hoping it is something that can be treated - not neurological. The Feliway arrives today so that should help them feel more comfortable in the home and not stress out.
At this point we're unsure of how to coax him into using the box for #2. Usually after a couple days being boarded they remember to ONLY go in the boxes.