+CIPDISCONNECT is when browser (or any client) closes connection. You should call CIPCLOSE after getting CIPDISCONNECT from ESP - at least I think that order should be.
But at this moment, there is a bug in releasing connection-contex resources and this causes to wdt_reset, check few post ealier, I had written about this too. When I call CIPCLOSE=connection-contex-id and after that, client connect again and send data to ESP next thing that happens is wdt_reset ...