Mobile account losing admin privileges in macOS if disconnected from domain

Question

I am able to join the Mac to the domain and the mobile account created fine, also able to administrate the Mac using the domain accounts.

But if I disconnect the Mac from the server or if the Mac unable to reach the server, the existing mobile accounts act as a regular user account, not an administrator account.

I want the existing mobile accounts to retain the same access level even when the Mac is disconnected from the network.

Example:

Username : Shiva
Member of : 'Domain Admins' Group
Activated the "Allow administration by = Domain Admins", under Directory Utility.