Since the 3.8 update (still present in 3.8.2) Android devices running Oreo on Nexus 5X are virtually unusable for internet connection when connecting via Wifi (5Ghz). The Wifi connection is established but the android device regularly reports no internet connection.
I have tried with and without DNSSEC and with and without forwarding which seems to change the severity but not drastically.
Note that for 3.7 series I had to add the following to get reasonable behaviour with the Nexus 5X otherwise the device kept jumping from 5Ghz to 2.4Ghz. When 2.4Ghz was disabled it kept dissaccociating completely. With the low ack set to 0 it was fine though.
option disassoc_low_ack 0
Other devices are also having issues since 3.8 but none as bad as this. Wired devices don’t seem as badly effected.