I see there are still lots of post on DFS channel drops and some devices not even working. DFS is a tricky feature and for users who live in the following environments DFS just might not work.
1 You live in an urban setting.
2 You live within 20 miles from civilian and military airfields
3 You live within 20 miles of a NOAA weather site.
4 Live in downtown or apartments were neighbors next door own microwave ovens.
5 Apartment complexes
6 Urban cameras on every corner.
7 Mini microwave dishes on building and street corners
8 Any source of microwaves close to your router.
Best place for good results is out in the middle of nowhere where none of the above is present.
I live where the main airport and military base and NOAA radars are 20 miles west. I have small airport with radar 5 miles north. I have a military radar site on mountain 10 miles s.e. I have aircraft flying over the house which can and does reflective radar waves down to the ground and as well back to source. DFS is not reliable for me so I don`t expect good results. Here is a link from ASUS which explains how DFS works in their routers.
https://www.asus.com/support/FAQ/1045936
Just my experience on the DFS issue