Well, the NTP address can potentially affect the response, especially if the controller can’t reach the NTP server and will have to periodically re-check the NTP server. I suggest leaving all options at their default values (i.e. use DHCP, don’t change NTP), and see if it’s still unstable.
Regarding MAC address: prior to OS 2.2, there is no MAC chip on the controller so the MAC address is software defined. To distinguish multiple controllers on the same network, the Device ID is used to differentiate the last byte of the MAC. Since OS 2.2, an ID chip is added so that each one has different MAC address.