Used to experience something similar... Not sure what I've done or not done, or what the neighbourhood has been doing, but the below config on 19.07.2 has seen me through a month of run time without any problem:
config wifi-device 'radio1'
option type 'mac80211'
option hwmode '11g'
option htmode 'HT40'
option legacy_rates '0'
option channel '1'
option path 'platform/ahb/18100000.wmac'
config wifi-iface 'wifinet1'
option network 'lan'
option ssid '***ssid***'
option device 'radio1'
option mode 'ap'
option key '***key***'
option encryption 'sae-mixed'
option wpa_disable_eapol_key_retries '1'
option ieee80211w '2'
For 5GHz, the non-CT version of firmware and drivers are being used.
Cheers.