slow internet timecapsule

I just bought the new TC (Tower model) I also have a TC frpm 2009 that still i functioning.

When I use the new TC internet sometimes gets really slow and i even loose my WIFI network. If i switch back to the old TC the network and the internet runs smoothly and fast.

Is the nes TC broken or do I have to make any changes in my settings to get the new one to work.

As I mostly the new TC works fine but now and then it deosn´t.

Help me!