Thanks for the explanation - makes sense. Still, it would be helpfull if the ESP would return an error and not just use the channel of the sta, regardless what the CWSAP command called for.
Anyway, if running in sta+ap mode is apparently no good, what else to do about these sudden "loss of connection" problems? The behavior is really strange since it is intermittent: it works for quite a while and then suddenly, no response to pings anymore (though the ESP is still alive, it responds to AT commands). But then, after some further while the ping requests get answered again. And it goes on like this off and on and off...
I'm pretty sure it is not due to my AP or DHCP server in use. Too many people in this forum have reported similar observations. I used WireShark on a WLAN-controller to check what's going on "in the air", especially if my AP didn't forward ESP packets on or off the Wireless-realm to the wired network. But everything looked absolutely ok, just that the ESP from time to time didn't respond to ARP request ("who has IP address X.X.X.X? tell Y.Y.Y.Y") and after that things timed-out...
Please have a serious look into this. Without a stable operation the ESP is just a nice toy to play with... Thank you!!
JoeK