Not a bug. Some players are hard headed/set in their thinking and one session with the psychologist is not enough. Tap +1 again and his morale will go to Superb. I usually leave such tough nuts alone. "Very good" is good enough to play. Spending 2 morale boosters to go from "Very good" to "Superb" is not worth it.

And it's not new, I have seen it from the day I started playing.