Hello, my name is***** static can build up in the microprocessor, causing it to do funny things. I suspect that is what is happening with your keyboard.Unplug it for one full minute. Turn the power switch on during that time.If that doesn't do the trick, turn it off. While simultaneously holding the highestwhite key and the three highest black keys, press the power button to turn it on. Please tell me the results.
Since I posted the question I turned off at the plug for about 5 minutes turned it on again and it seems to be back to normal. If it does it again I will now know what to do so many thanks for your help.
You are very welcome. Static gets built up in the microprocessor, and it confuses the power; It starts going in different routes erratically, and it can stick to the same wrong route, which is what you were experiencing. It's easily cleared by draining any residual power. It's also caused by cold weather, dusty conditions, and sometimes when it's too hot.
Thank you very much for your help Michaela