I am having the same problem with scrolling on all 3 wdtv live players i have, after updating the firmware
& the issue with the brightness.
The fix I went with was roll back the firmware to the previous one until they fix it
This double key / repeat key problem also exists in earlier version of the firmware. Initially, I thought it was the remote. But swapping the remote from my other WD box, I realize it was likely the box itself.
From trial and error, I found that doing a reset using the hole (not factory reset using menu, but paperclip in the hole next to the USB plug on the side); it will put a stop to the double key / repeat key. I just confirmed it again since mine was doing it too much.
I used to reset every firmware upgrade. But it is such a pain to redo everything I stopped that. However, having done reset like that, I found that the process of upgrading seem to bring it on, the menu reset doesn’t clear the double/repeat key, but reset via the hole clears it. The double/repeat key problem does return. I know for sure upgrading is a process that causes it. I am however not sure it is the only process to get it.