The devices that cannot be upgraded (4Pro, Motion) are still successfully using the same NTP server with the name and it's working like a charm.
Hello Patrice,
have you the local ntp-server running at the Shelly 4Pro??? Have you blocked the internet access of these Shelly 4Pro's, or do they have still internet access? If they have still internet access then the time is still coming from the internet (time.google.com) and not from the local ntp-server.
On my Shelly 4Pro's (without internet access) the ntp setting (with IP-address) takes no effect. After reboot/power loss the there is no time shown any more. And because of this no power metering is possible, too.