If all the tests pass, I'm not sure what to suggest. Make sure there is no card in the slot.

Keep it powered up in and don't let it get too hot.

If the problem follows a powerdown it would suggest that the battery needs changing.

Otherwise it has to come for service. Or, don't use that preset.

You could try a software update, but that should not be necessary. I assume you've tried a complete re-init (hold down SETUP at power up).