I think I've isolated the issue to this harness. It is the one that when unplugged indicates 'tailgate ajar.' With all of the other plugs from the tailgate in I removed this one, truck indicated 'tailgate ajar.' I left the normal tailgate plugs in and replaced the harness with the Ford provided 'tailgate delete' jumper, and it still says tailgate ajar. Presumably this thing is supposed to, in part, trick the truck into thinking the tailgate is closed and it does not do that.