I also have this problem with the Venton HD eco. I tested a VU+ duo a couple of weeks ago with the latest Openvix, iniatialised drive and all was perfect including the timeshift pause. A couple of days ago I flashed a Venton HD with openvix 3 2 037 and no live pause. I know you can remedy this to a degree by assigning a button to use for timeshift before you will be able to use it. To do this:
Menu-> Setup-> System-> User Interface
At this point choose 'Button Setup' and then press the button you would like to use for starting timeshift (eg: the 'Play' button). Now you will be presented with a list- choose 'Info Bar' and then 'Start Timeshift'
Pause button will pause and Ok button will play again. but why not the same as the VU duo pause and play button?