This device is set up as an access point.
This device will often drop clients connected on the 5GHz WiFi connection and I have a devil of a time reconnecting them (soft and hard reboots usually don't work - not sure what really fixes the problem when it does finally reconnect.)
Here is a log of an android phone trying to connect to this access point:
Fri May 24 22:58:13 2019 daemon.info odhcpd: Using a RA lifetime of 0 seconds on br-lan
Fri May 24 22:58:20 2019 daemon.notice hostapd: wlan1: AP-STA-DISCONNECTED 7c:d9:5c:b3:82:69
Fri May 24 22:58:20 2019 daemon.info hostapd: wlan0: STA 7c:d9:5c:b3:82:69 IEEE 802.11: authenticated
Fri May 24 22:58:20 2019 daemon.info hostapd: wlan0: STA 7c:d9:5c:b3:82:69 IEEE 802.11: associated (aid 1)
Fri May 24 22:58:20 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 7c:d9:5c:b3:82:69
Fri May 24 22:58:20 2019 daemon.info hostapd: wlan0: STA 7c:d9:5c:b3:82:69 WPA: pairwise key handshake completed (RSN)
ath10k depends to a huge extent on the firmware blob, uploaded to the wlan cards - there have been quite significant updates in upstream ath10k firmwares (albeit mostly for the newer chipsets) and there is ath10k-ct in master, both are worth having a look at.
Depending on your region. frequencies in the 5 GHz band might be required to do DFS, which has implications on the reliability to use them (and the DFS detector might trigger for 'normal' interference as well).
Very likely, (weather-) radar is the exact reason why devices must vacate a radar encumbered channel immediately; radar is the primary (licensed) user of those frequencies, wlan is only allowed to re-use them if there is no radar in sight.
I swapped locations as @psyborg suggested and it did not help. I reinstalled the firmware and it fixed it (temporarily). In my infinite wisdom, I tried to spread my channels around so that they would not overlap. That broke it. I then changed all (4) of my access points to b: 36, 40, 48, and 136. I rebooted the devices and they are all working fine.
I believe there is an issue with channel selection, but it is more restrictive than suggested before. I think what really fixed it was to set the channels lower and ensure to reboot if you get the "wireless not associated" error.