Am I imagining things, or does Flute Phi not respond to pitch bend? I get nothing from either the key bend up or the slider bend down, although these work fine for other sounds.

That is identical to what I am experiencing.

I'm glad I'm not the only one with the MacGuffin sound changing. Wondered if I was imagining it to start with.

Symptoms are that the timbre varies, sounds like a filter changes

To replicate:
Blow a note.
Don't move a muscle, so as not to alter any of the positional sensors.
Wait a few seconds.
Blow again (at same strength as before)

Note that playing continuously, or with short gaps between notes does not seem to make this happen.