Metronom click problem in control room

Hi,

Cubase : 6.0.4 32 bits & 64 bits
OS : Win 7 PRO 64 bits

1/ Create a new project whatever the frequency and resolution is.
2/ activate the “click” in the transport bar
3/ open control room and activate the click on the “headphones” output
4/ press play => the click get out into your headphone, OK
5/ stop play
6/ activate now the click on the “speakers” output in the control room (now click is activated for “headphones” and “speakers” output)
7/ press play => the click get out into my headphones and my speakers but some beats of the click are “jumped” randomly !!!
8/ deactivate the click on the headphones and let it on the speakers output of the control room => all beat of the click are present in the speakers output.

Apparently, if we activate the click on both headphones and speakers output of the control room, some beats of the click are missing randomly.