Radio/Stereo: Fault when entering radio code.

[Toplights]

Hi all having recently recharged my battery i am having an unusual fault while trying to enter my radio code ( which i have done many times before). I enter the first two numbers on the keys and they are ok, i then try and enter the third number which is a 5 and the key doesent produce it, it produces 2 or 4 but not 5. Has any one encountered this fault before. off course i get the usual off message and then have to wait 2 hours before i can try and reset it. Get you thinking caps on lads i need help, and thanks.