This is a weird one where Google isn't really helping me.
The user essentially loses his administrator rights when he leaves the office. Once he is back, we has administrator rights. I checked when he is in the office and the "Allow user to administer this computer" is checked but greyed out even once I unlock it.
Computer is properly bounded to the domain.
Added "Domain Users" group as a member to "Allow administration by:"
Macbook Pro (15-Inch, 2019)
OS: Mojave 10.14.6