Weirdly Specific Playback Bug

Good morning, I found this bug while transcribing a trumpet part:
Only when using the Muse Brass - Trumpet sound font, a B3 (A3 concert pitch) followed by a G#4 (F#4 concert pitch), only at forte or louder, there is another sound playing on top of the playback. It sounds like a trombone, or maybe just the same soundfont playing a concert B2 over the first note and a very flat concert A3 over the second note.

I've noticed this only happens in this specific situation, and does not happen:
1. At dynamics mf or below
2. If there is a rest of any length between the two notes
3. If the notes are in any other octave
4. If any other instrument or soundfont is used
5. If either of the notes are shorter than a quarter note

Given how specific the circumstances are, I'm not surprised it hasn't been noticed before but it's probably something to take a look at. Hopefully a pretty easy fix.