I hope that this answer will appear because it is a solution to the above problem. I apologize if I have not used the response mechanism properly.
The solution I found is to hold a delay after activating the softAP mode and has been obtained from this message
https://github.com/esp8266/Arduino/issues/1384
... Configuration AP mode (IP etc)
WiFi.softAP("miSSID", "mipassword");
delay(10E3);//This delay makes the AP mode works properly.
... more code.
"Wifi evt: 7" debug messages continue to appear after connecting a client, but the operation is still correct as expected. In my case it is for a UDP server, although so far I have only checked the Web server of the sample program. In case of finding some other problem I will also put it here, in case someone helps you, as well as the possible solution.
Thank you very much and I hope this can help someone.