My first question would be whether the battery contents got onto the
circuitry inside or was confined to the battery compartment ?

I would carefully clean up any residue inside the radio. Assuming the damage
was only in the battery comopartment, carefully clean off the battery
contacts so you get a good connection. If the connection is not good metal
to good metal you are not getting sufficient power.

Since you say the radio still works, I assume that the battery compartment
was the only place corroded. You could clean off the contacts with a pocket
knife or some fine sandpaper. I would avoid using liquids in there, but if
you do, just use a qtip dipped in a little bicarbonate of soda or some
rubbing (isopropyl) alcohol, then dry the contacts very well. HTH mm