I have hit this problem several times – a member server changes from “Domain” to “Public” or “Private” network after reboot.

Permanent fix I have found

Add below registry key and reboot your member server. Once below reg key is set up, your server will keep sending requests to Domain Controller until it is found.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NlaSvc\Parameters

Add a DWORD parameter : AlwaysExpectDomainController

Set value to:1

H/T: https://superit.in/dmz-rodc-is-going-in-public-network-profile-after-reboot/