[SteveCG]

I don't know this model, however I've found that jumbled tuning can happen when the preset pots have developed (mechanically) poor contacts between the wiper and the tracks. Also, is there a voltage regulator circuit designed to provide a constant voltage to the preset pots? This will use a zener diode that may have gone electrically noisy; hence the tuning voltage would be jumping around giving a jumbled receiving frequency operation.