XPS 9550: wifi and bluetooth interference

Hello,

I have an XPS 15 9550 equipped with a Dell 1830 wireless card. I have a problem when wifi and bluetooth are both enabled: when I'm connected to a 2.4GHz 803.11n network the bluetooth doesn't work. I use a portable Bose speaker and I cannot stream music to it (e.g. from Google play music or spotify), it continuously scatter. Using internal speakers it works fine, as well as when I'm connected to a 5GHz AC network.

I disabled "bluetooth collaboration" from advanced options of the credit card, because when it was enabled also the wifi connection was unstable if wifi and bluetooth were both enabled.

Dell Support doens't know how to solve it.