I'll follow Tweeterguy on this one, I have a lot of those in the field with no issues like you describe, but recently I had a RTI remote where certain buttons stopped working, like enter, CH+ and so on...

The wife called up and said "the remote is not working, send some to look at it", and when one of my techs showed up, she said that no one dropped it, nothing was spilled on it, etc...

So when I call up the Husband, who is a friend of my boss, to discuss an on going CCTV project at his business, he tells me "hey, did one of your guys get to my house yet to clean the remote"?... So I ask, "clean the remote"? He says, "yeah, clean it out or something, my wife knocked over the kids juice box on the remote last night & now its all funky"....

Anyway, it is possible you got a defective unit, not likely, but possible.

Did you spill anything on the remote? Press any of the buttons shockingly hard? Did you have poor response from the RF base, so you repeatedly have to press the same buttons for responses?

I guess im just shooting in the dark here, but I do find it strange to just stop working on single buttons.