This isn't a bug. It's ... I'm not quite sure, actually.
Anyway, you know how an octave is 12 steps and the Noise channel has 16 tones? I was tweaking a percussion part by using the Transpose Octave keys (effectively adjusting the notes by 4 steps at a time) when I noticed that it would only shift so far up or down. As if the actual stored note is in the usual 8-octave range but the note shown in the UI is wrapped to the last 4 bits only. Is that how it works internally or something?