@adm - My apologies! My Quad Plus does work when pressing the REW key when watching live TV. I have permanent timeshift enabled on this box and it's set to kick in after 10 seconds on the channel. I think what I was remembering was when I had PTS turned off. In that instance you have to press play/pause to kick off timeshift. I have similar issues as you with the < and > keys to jump over programme boundaries - works sometimes and too easy to accidentally clear the buffer.
The freezing I see occasionally when watching either timeshift or recorded programmes, which I can clear with the number keys, must be another issue.