Some devices don't recognize 5ghz networks on some or all DFS channels.  This forces the devices to 2.4 ghz which results in inadequate performance.   Devices that appear to be affected are Roku and Firestick devices.  In my case, the 2.4 ghz speed is inadequate, whereas 5 ghz works fine when Eero assigns a lower channel number.  At channel 100 Rokus can't even see 5ghz.