Hi from the UK.... A very wet and cold UK!

I have a new 3.7 V6 engine which is showing an intermittent 'check charging system' warning.

The alternator is healthy - measuring a 13.7 volt output at tickover.
The battery is healthy under a load test.
The car is driving, starting and operating normally.
All the fuses are intact.
The alternator belt feels tight enough.
I've disconnected the battery for half an hour to see if the ECU might reset. No change.
I've hooked up an OBD reader - no fault codes.

I assume it must be the voltage regulator which I guess is within the alternator.

Any thoughts guys?

Many thanks.