I have a Pebble Steel, and the "right-hand" (up/select/down) buttons do not reliably work properly.
The "down" button always works (as does the "back" button on the "left" side of the watch). The select and up buttons only work if I first press the down button (which performs the down action.) after I "wake up" the watch by pressing the down button (the back button does not "wake up" the buttons, though it functions properly), I can use all three nav buttons properly for a short period of time, until I let the watch alone for a bit; at which point the up and select buttons stop working again, until I press the down button. This behavior occurred on the pre-Time firmware, and also occurs on the v3.9.2 Time firmware. It has survived hard resets as well.
Is there anything I can do about this odd behavior? I can work around it in most apps, but a couple of apps I have do non-reversible things if I hit the Down button.