Hi Mark, do you have tame Technics engineers local to you? the first thing I would do is to download the service manual for the KN7000 and get them to remove the control panel assembly,remove the rear cover and remove the central panel,it may be the contact strip is damaged or something as simple as a buid-up of dust,as you have used a contact spray/cleaner you may have caused further damage as these contacts are made of silicone and or polly-rubber which does not take kindly to the type of spirit fluids used in the cleaner sprays.
A simple thing you can try your self is to use a can of compressed air (air duster from Radio Shack) use this around the bottom row of switches blowing in all directions,it's a slim chance but worth a try,if not you will need an engineer.
Sorry I could not send you good news ,hope you have success soon regards John. (ex Yamaha and Technics dealer/engineer)