Could be anything, but a "click" is not good, because that indicates a collision. If you have magnification, I recommend to inspect the edge. If there is a problem, you will
spot a small chip.
What you can do, is to bring down the spot, so it lies just below the surface. You may need to repeat it every few years as the rest of the surface wears level with the dimple you made.
To make such a dimple, take a needle or a sewing pin, raise a bit of slurry and start scratching the affected spot with the pin, with the shortest strokes possible. Even on a hard stone, you'll be surprised how quickly you can work your way down in a Coticule.
One of the theme pictures is a photo of a Coticule saw:
Because of the highly localized abrasion, the saw went faster through the rock than you might expect. With only a needle point, it will be even faster. So do rinse and check for progress regularly. I would not create a dimple deeper than 1 mm. You won't feel the dimple at all while honing.
ship the hone back to Ardennes and they will send you a replacement, but I personally wouldn't be bothered.