IWC (3904) Chronograph - Click when winding

[Gigaton Punch]

Hi all,

I had a question regarding my IWC 3904 portuguese chronograph classic. Once in a while, when I wind the watch, I first hear a light click before the usual winding. The click feels like a mechanism of some sort, but not sure if this is supposed to be normal or not. This happened to me when the chronograph is not running. To replicate this click, I've been randomly winding my watch throughout the day, but I only experience 1 out every 25 winds, or so. No other issues with watch; keeps good time.

Is this normal?

Thanks in advance.