I have seen the same errors (hostapd: handle_probe_req: send failed) when I tried to run multiple SSIDs on the same interface.
Yes, I discovered that multiple SSIDs is completely broken. Not even two WPA-PSK networks can operate on one SDIO radio. But even with one SSID, the 802.1x cannot proceed correctly, it will get stuck with CTRL-EVENT-EAP-RETRANSMIT2 phase.