I'm having a hard time pinning this down.  I'm seeing this on an SB2.  It _seems_ to happen just when bitrate limiting is set, but I couldn't say that for certain.

What I often see when doing a hold-pause is that the display immediately flips to the date/time screensaver, but music continues to play.  Play/pause/unpause/skip/power_off all work as expected and all work instantly.  Stop, though, works only sometimes.