Update:

I add approximately 75ml which overflowed the radiator.
So that is an indication there is no leak.

I have had the bike for about 2.5yrs and no problems.
I have a workshop service manual for it, but don't see any solutions.

Could it be a false-positive, due to a temporal fault with a sensor?
or is their further testing recommended?

Any suggest a reliable meter monitor to watch the temperatures of critical systems, some thing that isn't took expensive

Thank you folks, much appreciated.