Get-LocalGroupMember - Failed to compare two elements in the array.

It appears that if you have domain groups added to a local group and then move the server to a workgroup before removing them Get-LocalGroupMember no longer works and instead throws an exception ‘Failed to compare two elements in the array.’. I am seeing this on Server 2016 Core, I have not tried on any other editions. I found this while building a server in one domain that needed to move to a different one.

Steps to reproduce

• Join a Windows Server 2016 Core server to a domain.
• Added 3 domain groups to the local administrators group.
• Moved the server back into a workgroup.
• Ran Get-LocalGroupMember -Group Administrators

I’ve reproduced this on two servers.

Expected behavior

It should return the group members as it would prior to moving to a workgroup and just display the unresolved SIDs for the old domain. Then ideally allow you to reference those unresolved SIDS for Remove-LocalGroupMember.

Actual behavior

Throws an exception.

Environment data

> $PSVersionTable
PSVersion                      5.1.14393.206
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.14393.206
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1