Slow respons open mixwindow..

Hi,
This phenomena has occured in earlier versions of Nuendo, It seems to come and go with the updates, it has been a while but showed up in N10 again…

When using F3 to open my mixwindow I have to enter TWICE instead of just once…
A little problem but not when you are used to just get it done.

Is this a bug?
Micke.