I didn't particularly take note what I fought. It was not like I expected this to happen. In any case, I had Serina and the Bunny active, with Lima and the Elf guy passively participating.
If you can't replicate it, it might be possible an engine error somewhere. A lost pointer or something like that.
When going at NG+, I noticed a statue at the kitsune shrine, which swapped constantly appearance. It also sells "Lufillia's Favor". Is that not part of the normal line up? Or because this is on hard mode?