You know what's interesting about 17,185? It's 0x4321 in hexadecimal! So we know that it's a fictitious source. When I hit a physical button on a B&N Glow21, I get 2 as source id. Normally that's what you'd do with GPIO buttons. And they'd use a keylayout.
Try this just to double check, you don't have to be rooted.
Code:
$ cd /system/usr/keylayout
$ grep VOLUME_UP *
Do you see anything that doesn't say 115? No? I didn't think so.
A lot of Onyx software is kept consistent across models, but I'm guessing that you've got something on your Nova Air that isn't on my Poke3.