Same bull$hit occurring. Some clients cannot connect to WLAN0 (5 GHz) after DFS detects radar and switches frequencies.
The only conclusion I can come to is the version of marvel firmware, DFS, or hostapd is broken in 18.6.2.
Tue Apr 30 14:21:43 2019 kern.info kernel: [11060.422071] ieee80211 phy0: radar detected by firmware
Tue Apr 30 14:21:43 2019 daemon.notice hostapd: wlan0: DFS-RADAR-DETECTED freq=5500 ht_enabled=0 chan_offset=0 chan_width=3 cf1=5530 cf2=0
Tue Apr 30 14:21:43 2019 daemon.notice hostapd: wlan0: DFS-NEW-CHANNEL freq=5745 chan=149 sec_chan=1
Tue Apr 30 14:21:43 2019 daemon.notice hostapd: wlan2: DFS-RADAR-DETECTED freq=5500 ht_enabled=0 chan_offset=0 chan_width=3 cf1=5530 cf2=0
Tue Apr 30 14:21:44 2019 kern.info kernel: [11061.043086] ieee80211 phy0: channel switch is done
Tue Apr 30 14:21:44 2019 kern.debug kernel: [11061.048115] ieee80211 phy0: change: 0x40
Tue Apr 30 14:21:44 2019 daemon.notice hostapd: handle_probe_req: send failed
Tue Apr 30 14:21:44 2019 daemon.info hostapd: wlan0: IEEE 802.11 driver had channel switch: freq=5745, ht=1, vht_ch=0x0, offset=1, width=3 (80 MHz), cf1=5775, cf2=0
Tue Apr 30 14:21:44 2019 daemon.notice hostapd: wlan0: AP-CSA-FINISHED freq=5745 dfs=0
Tue Apr 30 14:21:44 2019 kern.debug kernel: [11061.143732] ieee80211 phy0: change: 0x20
Tue Apr 30 14:21:46 2019 kern.debug kernel: [11063.603763] ieee80211 phy0: staid 1 deleted
Tue Apr 30 14:21:46 2019 daemon.info hostapd: wlan0: STA f4:5c:89:**:**:** IEEE 802.11: associated (aid 1)
Tue Apr 30 14:21:46 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED f4:5c:89:**:**:**
Tue Apr 30 14:21:46 2019 daemon.info hostapd: wlan0: STA f4:5c:89:**:**:**WPA: pairwise key handshake completed (RSN)
Tue Apr 30 14:21:47 2019 kern.debug kernel: [11063.941877] ieee80211 phy0: staid 2 deleted
Tue Apr 30 14:21:47 2019 daemon.info hostapd: wlan0: STA 44:39:c4:**:**:** IEEE 802.11: associated (aid 2)
Tue Apr 30 14:21:47 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 44:39:c4:**:**:**
Tue Apr 30 14:21:47 2019 daemon.info hostapd: wlan0: STA 44:39:c4:**:**:** WPA: pairwise key handshake completed (RSN)
Tue Apr 30 14:21:47 2019 daemon.info hostapd: wlan0: STA f4:5c:89:**:**:** IEEE 802.11: authenticated
Tue Apr 30 14:21:47 2019 daemon.info hostapd: wlan0: STA 44:39:c4:**:**:** IEEE 802.11: authenticated
Tue Apr 30 14:22:02 2019 daemon.info hostapd: wlan1: STA 60:f8:1d:**:**:** IEEE 802.11: associated (aid 7)
Tue Apr 30 14:22:02 2019 daemon.notice hostapd: wlan1: AP-STA-CONNECTED 60:f8:1d:**:**:**
Tue Apr 30 14:22:02 2019 daemon.info hostapd: wlan1: STA 60:f8:1d:**:**:** WPA: pairwise key handshake completed (RSN)
Tue Apr 30 14:22:03 2019 daemon.info hostapd: wlan1: STA 60:f8:1d:**:**:** IEEE 802.11: authenticated
Tue Apr 30 14:27:05 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 60:f8:1d:**:**:**
Tue Apr 30 14:27:05 2019 daemon.info hostapd: wlan0: STA 60:f8:1d:**:**:** IEEE 802.11: disassociated due to inactivity
Tue Apr 30 14:27:06 2019 daemon.info hostapd: wlan0: STA 60:f8:1d:**:**:** IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Tue Apr 30 14:27:06 2019 kern.debug kernel: [11383.181365] ieee80211 phy0: staid 4 deleted
Tue Apr 30 14:36:52 2019 daemon.info hostapd: wlan2: STA 00:06:80:**:**:** IEEE 802.11: associated
Tue Apr 30 14:36:52 2019 daemon.notice hostapd: wlan2: AP-STA-CONNECTED 00:06:80:**:**:**
Tue Apr 30 14:36:52 2019 daemon.info hostapd: wlan2: STA 00:06:80:**:**:** WPA: pairwise key handshake completed (RSN)
Tue Apr 30 14:36:53 2019 daemon.info hostapd: wlan2: STA 00:06:80:**:**:** IEEE 802.11: disassociated
Tue Apr 30 14:36:53 2019 daemon.notice hostapd: wlan2: AP-STA-DISCONNECTED 00:06:80:**:**:**