Same issue happened to me, got an email saying Nianzou is happy I've been playing him as a BPD, then a second email saying that even though he wasn't being played as a BPD, he is still happy (I played him as a BWM for 20 minutes in one game). However his morale has now reduced massively and it says he is unhappy that I haven't kept my promise and played him as a BPD. Very frustrating bug.