You need ap_isolate=1 in hostapd's settings to prevent the Wireless driver to perform low-level bridging of the wireless frames coming from Wifi and sent back to same Wifi which short-circuits the network stack and the bridge br0.
But ap_isolate alone results in Wifi client isolation: it can't see anymore other Wifi clients without additional settings.
The double ampersand or "&&" executes a following command once the preceding one finishes successfully. So I would try writing a restart for sshd after tcpdump is done to reset the ssh interface.
tcpdump -i eth0 && sudo systemctl restart sshd