Odd harmonic in playback

I’m getting some odd harmonics in m. 39 of the attached piece.


Instrument is Olympus Choir Legato Ah (doesn’t seem to happen for GM instruments)
I also don’t notice if I play solo the bass OR the tenor, but I do notice it if both of them are playing.
How Do I Love Thee.dorico (2.0 MB)

What’s going on?