SCS3 as a system? Or just SCS3d with a regular mixer?

Right. Traktor is generally very well behaved, and doesn’t crash because (for instance) a device gets disconnected. If you’re getting freezes, and neither Traktor nor the DaRouter software produces an error, I’m going to guess a problem with the audio interface.

I had that problem with a old traktor 1.2.x version… After I upgraded to the last version I never had that problem anymore…
I’m using Windows XP SP3