If only one device is experiencing issues, it may be due to the way some devices handle ARP after entering sleep mode (though this may not be the only cause).
We recommend that, when the issue occurs again, you check the device’s ARP table to see if entries for other devices on the same subnet that are actively pinging or communicating are present.
# On Windows CMD
arp -a
# On Linux
ip neighbour
If it’s confirmed that the ARP entries are missing, you might try enabling Proxy ARP and Multicast-to-Unicast to see if this resolves the issue.
# Enable the Proxy ARP
uci set wireless.wifi2g.proxy_arp='1'
uci set wireless.wifi5g.proxy_arp='1'
uci set wireless.wifi6g.proxy_arp='1'
uci set wireless.wlanmld2g.proxy_arp='1'
uci set wireless.wlanmld5g.proxy_arp='1'
uci set wireless.wlanmld6g.proxy_arp='1'
# Enable the Multicast to Unicast
uci set wireless.wifi2g.multicast_to_unicast_all='1'
uci set wireless.wifi5g.multicast_to_unicast_all='1'
uci set wireless.wifi6g.multicast_to_unicast_all='1'
uci set wireless.wlanmld2g.multicast_to_unicast_all='1'
uci set wireless.wlanmld5g.multicast_to_unicast_all='1'
uci set wireless.wlanmld6g.multicast_to_unicast_all='1'
uci commit
reboot