Not sure how I made this happen, but when Alma Reynard (target) and Orson Mills go to bed in Hawke’s Bay, Orson levitated into the air I could still assassinate Alma and finish the mission, but wow was this unexpected! The glitch has happened temporarily with the Alma model as well.
I note that I did get the NPC’s attention, hiding behind the couch in the bedroom. He walks over to inspect, then returns to bed. Maybe this contributed to the glitch.
Wondered if anyone else has had the same thing happen on Xbox one or other platforms.