I know that play/pause look like it's a single button, but the remote actually has seperate contacts for both. One on top for play, one on bottom for pause.
If you're hitting the button square in the middle or towards the top, it may just be registering it as play - hence the STB recognizing the remote command and showing the progress bar but nothing happening..
Wow, I would have never thought of that, for whatever reason I have always done it the "right" way I guess. And I tested what you wrote just to see, and sure enough, I got the same result. Good job!!!!