Wi-Fi hangs on Mikrotik RB951Ui-2HnD

Guys could you please guide me how to debug Wi-Fi operation on the router?
It hangs once a week or two on average and this has been happening for me on all 18 and 19 releases. Currently the router is on 19.07.2.
When it happens I can always logon via Ethernet and see what's going on but for now I am unsuccessful finding the root cause. I have configured remote logging and there are no clues in the output.
'wifi up' command always fixes the situation.
Am I missing something? Is there something I should take a look?
Here is wireless config:

config wifi-device 'radio0'
option type 'mac80211'
option hwmode '11g'
option path 'platform/ar934x_wmac'
option channel 'auto'
option legacy_rates '0'
option country 'UA'
option htmode 'HT20'
option log_level '1'

config wifi-iface 'default_radio0'
option device 'radio0'
option network 'lan'
option mode 'ap'
option wpa_disable_eapol_key_retries '1'
option key '*****************'
option ssid '****************'
option encryption 'psk2+ccmp'
option disassoc_low_ack '0'

I have tried replacing stock wpad-basic with hostapd but it made no significant difference.

SoC has a small heatsink on it glued with a quality thermal adhesive. This does not guarantee that it does not overheat though.
It's worth noting that the same also happens for me with Mikrotik HAP Lite.