Ruckus Wi-Fi network experiencing latency spike and unstable wifi connection

our company is suffering from the latency spike and unstable wifi connection.

We have tried the following action to improve the situation:
- adjust Tx Power to "Auto" or "full" or "Min"
- Adjust radio channel range from all to 36-112, 149-161
- channelization from "auto" to 20
- only use 5GHz radio
- switch off some AP
- tune PoE power mode to 802.3bt/class5
- use WPA2 encryption method only
- disable RADIUS authenticate SSID
- Isolate wireless client traffic from other clients on the same AP
- Enable "Rate Limiting" to 80Mbps per client
- Disable Proxy ARP
- Enable Background scanning
- Enable OFDM
- Enable 802.11k

- test ping with same vlan as AP network

but seems no improvement and issue still exists.

we are using top of the line R850 AP with ZD1200, Cisco C9200L-48PXG-4X for PoE switch.

What is the problem? does the AP network too crowd? or the switch settings is wrong?

below are the switchport config:
interface TenGigabitEthernet1/0/37
switchport trunk native vlan 122
switchport mode trunk
power inline port priority high
power inline port 2x-mode
power inline port perpetual-poe-ha
power inline port 2-event
power inline port poe-ha
power inline police action log

end

the latency spike:
https://imgur.com/a/myZ6cnm

the simplify network diagram:
https://imgur.com/a/v1aFjN8