Multicast stops working after second group rekey

[Markus]

Hello,

I am running a hostapd with following setup:

interface=wlan0
bridge=br0
driver=nl80211
hw_mode=g
channel=5

ssid=xxx
auth_algs=1
wnm_sleep_mode=1
beacon_prot=1
ieee80211w=1
wmm_enabled=1
#wmm_ac_* like in example
ap_isolate=1
ieee80211n=1
ht_capab=[HT40-][GF][SHORT-GI-20][SHORT-GI-40]
dynamic_vlan=1
per_sta_vif=1
wpa=2
wpa_psk_file=/etc/hostapd/hostapd.wpa_psk
wpa_key_mgmt=WPA-PSK
rsn_pairwise=CCMP

In general it works. But I noticed that after two days multicast communication
fails for all stations. (mdns discovery stops working.)
At the time it fails I noticed in the hostapd log the rekey entries. The
default is a rekey every 24h. So I changed it to 5 minutes to check:
wpa_group_rekey=300

Now multicast failed after 10 minutes. (So the first rekey after 5 minutes
worked, but the second and any further rekey succeed according to log, but
multicast does not work.)

(I could increase rekey interval or disable it all together, but I guess thats
not recommended. ;) )

Deauthenticating the clients with "hostapd_cli deauthenticate" sometimes
recovers multicast for up to 10 minutes.
Not sure why it does not recover everytime.


Hardware is a ALFA  AWUS036ACHM with mediatek mt76.
Kernel is 6.6.37, linux-firmware from July.
Recently updated hostapd to latest git version.
All stations are affected, at the moment android devices and various smart
home devices from different brands.

Any idea what the problem could be?
Is it a misconfiguration or some bug?

Any help is highly appreciated.

Thank you,
Markus