So I have added pitch bend modification for Roland GS percussion channels to my editor.

It seems to be working most of the time, but strangely there are a few things that LOOK correct, but the pitch is always played back the same.

For example, the songs I am working on right now use various different pitched tambourines.  In one song, I could bend the tambourine down 6 semitones to get the desired pitch.  However, in the next song, no matter how much pitch bend I apply, it always sounds the same.  I compared the before/after contents of the uncooperative one, and I can see that the pitch bend range has been modified from 12 to 24, and that the bend amount has been changed from 150 to -8117.  These are expected.  Yet it does not play back with any change to the pitch.  I don't see anything readily apparent that is out of the ordinary.

Any idea what might be causing this?

I'm attaching 4 files: before and after of a working song (Tetroika), and before and after of a non-working song (Technotris).  Both songs the tamborine is the instrument in question, and in each it is on its own channel.