OnKeyPressed and OnKeyReleased on FR230, 235 & 735

hi,

I would like to catch the event of holding the Up or Down keys. Doing something like:
class MyDelegate extends Ui.BehaviorDelegate {
...
function onKeyPressed(evt) {
if (evt.getKey() == KEY_UP) {
// do something
}
else if (evt.getKey() == KEY_DOWN) {
// do something
}
}

function onKeyReleased(evt) {
//similar to the above
}

That works fine for all watches in the emulator, and also work fine on my physical Fenix 3. However, user reported that on their actual 230, 235 and 735 my app doesn't respond to the Up / Down key presses. I also experienced a similar issue in these devices trying to catch KEY_ENTER / KEY_ESCAPE keys, but in this scenario I could cope with catching the behavior OnSelect() / OnBack(). However, with the Up / Down key I really have to know when they were pressed and when released.
Is there something specific to 230 / 235 / 735 that should be done differently to catch these keys? Should I attempt to catch something from the extended keys? Is there a reason it works on the emulator but not on the actual device?

Thanks for the help!