I had a similar problem with an Android phone and VPN, and tracked it down to my DHCP server only serving primary DNS IP and no secondary. In this circumstance

I had a similar problem with an Android phone and VPN, and tracked it down to my DHCP server only serving primary DNS IP and no secondary. In this circumstance it seems Google automatically adds its own DNS resolver as secondary, which was causing DNS leaks. Try tunning tcpdump on your gateway looking at DNS and mDNS requests.