XPS 13 9360 wireless issue

I've had this problem since I purchased the laptop over 3 years ago but today my frustration level is extremely high: internet connection is continually being dropped even though my smartphone's wireless connection is fine (2 out of 4 bars).

Sometimes, the laptop can't find the network, sometimes, it connects ("connected, secured") but Network and Sharing window indicates "No Internet". Having read other threads on this issue, I've updated (Killer Wireless-n/a/ac 1535 Wireless Net Adapter), checked that BIOS is updated, etc.

Are there other things I should be checking/updating? Thanks.