I've had a FlightDeck for almost 4 years and haven't had any problems to speak of. Usually if the display starts messing up, check all the connections, change the battery to a fresh one and you might want to use a rubber pencil eraser on the little metal contacts and see if that helps.
I know the user's manual is pretty hard to follow at times. Of course you'll have to refer back to it if you remove the battery and reprogram the whole thing again.
I just thought of something. If you retaped your bars at any point in the recent past you may have jiggled the little wires loose that run under the tape up to the handbrake handle. There is a small plastic module with a ribbon cable that plugs into the side of the brake and maybe that is loose of not seated properly.
Hmmmm! Lots of variables there. Of course it may also just be a faulty unit too.
I've actually grown so used to the FlightDeck that if I ride my other bikes without it something seems to be missing. Jeez, I guess I'm too dependent on technology.
Although it is nice to know all the details of what's going on back there in the drivetrain.