It would help to know what the “once over” included.
Keith may be correct, and that can be tested.
It’s also possible that you have a bad radiator cap. That’d allow the coolant to boil at to o low a temp, and might not allow coolant to be drawn back into the engine when it cools and the coolant contracts (depending on how it’s broken).
It’s also possible that the radiator’s insides have some clogged tubes.With an infrared thermometer you can scan the radiator and detect hotspots and coldspots. They can be revealing.
You also might have a collapsed inner hose liner. New hoses are cheap.