Is it possible that some spray cleaner got into the controls?
I always recommend that users spray cleaner on a soft cloth then wipe the control panel.
I always recommend non-ammonia cleaners since they can crack and damage plastic.
Otherwise, the spray can get into the controls and lock it up or make it act odd.
If it does not dry out over time, it may need to be manually dried or blown out.
The keypad may be damaged or worn out, or control unit may be damaged.
If you or a friend decide to work on it, we have *critical* safety, disassembly, and troubleshooting info at our site, which is linked at our listing here on FixYa:
http://tinyurl.com/yzjozk