R15 DVR keeps indiscrimately activates and scrolls through the menu and changing channel.

My R15 DVR keeps keeps indiscrimately activating the menu and automatically scrolling through the channels, while channing the channels at the same time, the machine will stop on a non-channel (like a music channel).  Usually, you can not change back to the desired channel.  If you reset the machine, it will work for a while before eventually returning back to the same pattern of scrolling. The amount of time before the machine does this is not predicatable.  It could be a few days to a few minutes before the problem resurfaces.  If I am not able to get a satisfactorily solution, this machine will be returned to company. So, I do not keep incurring a change for it.