R75 Temperature gauge 'hunting' ?

Just bought another R75 cdt and on long motorway drive home noticed the temperture gauge hunting. 2006 reg with 80k miles.



Vehicle went up to 'almost' the right temp and then fell quite rapidly from 9 o'clock position to almost 7 o'clock. Then returned again quite quickly to 9 o'clock.



It was doing this hunting regularly on the journey. Fortunately it fell to the cool side rather than the hot side.



Any ideas appreciated - thank you..........

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