Thanks for your help. I downgraded to 5.11 and I am back. I before downgrade checked and see that it said e.g. 10 connected clients but no trafic Rx/Tx are zero(0) no trafic at all. I downgrade only RB433 that was making problems to me, that it had 2 WLAN cards one in 2.4 and one 5 (disabled) not in use. Other 2 RB and one PC I have no problems they run 5.15.
Thanks again for your help.
Below some info.
All interfaces are in the same bridge LAN.
Wireless (Atheros AR5413) running in 2.4
Wireless (Atheros AR5213) running in 5 - disabled not in use.