Some commands emit as long as you hold down the key, others only emit once per key press. This is determined by an internal (not user accessible) "continuous/single" flag (don't know the correct term). As far as I know, only Harmony Support can change that flag. Currently, on my Sony TV (KV-34XBR800), only the "Contrast" commands are set to single action. All the others (Brightness, Color, and Sharpness) are set to continuous action (like in your Brightness controls). However, when I click "Troubleshoot" next to my TV device, the S/W mentions that updates are available for this device. I have not done so. So maybe after the update, these commands will behave the same as yours, or maybe the faulty "Contrast" commands will behave properly.