E34 535i radio code, electrical oddity

[Steve Poole <stevep@xxxxxxxxxx>]

My wife's regularly-driven 1989 535i did something weird recently. 
Overnight it ran the battery totally flat for no reason that I can 
discern. I charged it and all was basically back to normal except for a 
couple of things. First, the antitheft LED (no alarm system) no longer 
blinks. Second, the radio won't accept the code. After the fifth digit 
it just beeps and continues to say "enter code" (or whatever the message 
is). I've had to enter the code in the past, and it took just fine.

Any thoughts? Thanks much.

Steve

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