Exactly, thats why I have fixed Channels for both 2.4GHz (11) and 5GHz (36) because ever since using the Linksys WRT1900ACS I had Radar Detection Issues on the 5GHz wifi with I think specially with width 80MHz and performance losses when streaming over Wifi, as described here cant-connect-to-5ghz-after-radar-is-detected-on-wrt1900acs or here 5ghz-radio-disappears-after-a-while-fritzbox-4040 for example (I was probably trying to use fixed channels in the DFS range back then). Interesting fact, can't remember ever having had those problems on my old OpenWrt 19.07 on a FritzBox 4040 though. But thats another story I guess.
My current wifi config
/etc/config/wireless
config wifi-device 'radio0'
option type 'mac80211'
option channel '36'
option hwmode '11a'
option path 'soc/soc:pcie/pci0000:00/0000:00:01.0/0000:01:00.0'
option htmode 'VHT80'
option cell_density '0'
option country 'FR'
config wifi-iface 'default_radio0'
option device 'radio0'
option mode 'ap'
option macaddr '00:11:22:33:44:55'
option ssid 'MY_SSID_5'
option encryption 'psk2'
option key 'VERY_SECURE'
option network 'WIFI'
config wifi-device 'radio1'
option type 'mac80211'
option channel '11'
option hwmode '11g'
option path 'soc/soc:pcie/pci0000:00/0000:00:02.0/0000:02:00.0'
option cell_density '0'
option country 'FR'
option htmode 'HT40'
config wifi-iface 'default_radio1'
option device 'radio1'
option mode 'ap'
option macaddr '00:11:22:33:44:66'
option ssid 'MY_SSID'
option encryption 'psk2'
option key 'VERY_SECURE'
option network 'WIFI'
Still running smooth 
mostly on 5GHz (Can tell because I have min. 4h+ MS Teams calls a day 
)