We have seen the situation where the router/internet modem is slower to come up such that the EZSrve cannot connect with an NTP server. I keep the modem (has built in router) on the same UPS as the PC so when power goes down I can still use the internet. When the EZSrve comes up after a power failure it has a functional internet access.
Check the time options on the EZSrve. Be sure the NTP option is still set after a power cycle. I don’t know when the EZSrve normally does a time sync but I should be able to set up a wireshark trace. Of course it will be relative to the time the EZSrve thinks it is rather than actual clock time.