My 2013 C4S has recently developed a weird problem and I wonder if anyone else has any knowledge about this.

From my understanding, the normal behaviour is this:
PDK, if in neutral, cannot be shifted into D unless you step on the brakes due to the shift lock. So with PDK in N, you can feel a slight click if you lightly step on the brakes to indicate lock release, and if you lift off the brakes you'll feel a click to indicate lock engaged.

This clicking should be at the very top of the brake travel.

Weird behaviour:

In addition to the normal clicking at the top of the brake travel, I have another double-click at about 1/4 of the brake travel down.

So basically if I start wit the PDK in N and brake fully depressed. As I lift off slowly, the PDK lock will do a double click when I'm 1/4 from the top. As I continue to lift off, it will then do the normal click at the very top.

Additional weird behaviour is that if I hold the brake at about 25% depressed (eg at red light) the PDK lock will sometimes actually continuously click on and off rapidly, with a rapid vibration and sound from the PDK stick.

Any ideas?

 

I own that model and have never noticed those quirks . I don't spend much time noodling around in neutral however.I would have the dealer look at the rapid clicking that does not sound right at all.