This is getting pretty annoying, had these problem for a couple of months now and not one update was able to resolve this issue. Whenever I am connected to a Bluetooth speaker, my WLAN connection seems to slow down and about every 4 minutes, my browser just gives up and displays a DNS probe error.
I use Pulse Audio Volume Control since the stock mixer in elementary OS is too basic. I can never connect to any Bluetooth device without loading
module-bluetooth-discover first. To sum it up, when connecting to a Bluetooth speaker, I first load this module, then connect to a device through system settings, then unload the stated module (unloading doesn't help with the problem either).
The OS can play sound well with minimal delay but it's just so annoying that I just suddenly have very slow Internet connection every couple of minutes. It renders the Bluetooth feature useless.