[Closed] Cannondale with 1.5" steerer, forks need attention

Hi, bit of advice really.
I've got a Cannondale Trail SL2 2010 model with RST Deuce Air 100mm forks, bike has been brilliant but now ready to sell, the forks themselves are great, really responsive to small bumps as well as bigger ones.
Only issue is there is a "loose headset" type bang at the front when going over rough ground. Had it checked out, not the headset, or wheel, it's the fork! I pride myself in honesty and wouldn't sell someone a dud.
Cant decide whether it should have a fork service, or sell with issue highlighted, or buy another fork. Ideally I don't want to be spending alot of money on a bike I'm selling anyway.
What do you think?