Fernando glad to see another one suffering on the same issue (joke !).
Acutally the watchdog is off on my OCS.
I'm working on this OTEthernet  sketch as a basis since it works fine.
I mean i can upload it constantly without any problem through the ethernet interface.
The ip used in this sketch is dynamic yes so i added it in Arduino programmer as a second address (see the video), so the first line is the static Ip (OCS) and the second one is the dynamic Ip (OTethernet)
The OTethernet sketch has 2 declarations
one in the void setup 
ArduinoOTA.begin(ip, "Arduino", "password", InternalStorage);
and a second in the loop : 
ArduinoOTA.poll();
I inserted them in OCS at the same place but no way.