Moving FSMO Roles from SBS to Server 2016

I am migrating from a Windows Small Business Server 2008 to a Windows Server 2016 and am looking at the final steps moving the fsmo roles over to the new server. I am following this guide (starting from 'Migrate FSMO to Server 2016). First step is to query who actually holds the roles with netdom

PS C:\Windows\system32> netdom query fsmo
Schema master               [sourceserver].[domain].local
Domain naming master        [sourceserver].[domain].local
PDC                         [sourceserver].[domain].local
RID pool manager            [sourceserver].[domain].local
Infrastructure master       [sourceserver].[domain].local
The command completed successfully.  

this looks as expected so I run the next commen (PowerShell on the Target Server)

PS C:\Windows\system32> Move-ADDirectoryServerOperationMasterRole -Identity [targetserver] -OperationMasterRole SchemaMaster
, DomainNamingMaster, PDCEmulator, RIDMaster, InfrastructureMaster

just it's throwing an error at me which I don't know what to make of.

Move-ADDirectoryServerOperationMasterRole : Unable to find a default server with Active Directory Web Services running.
At line:1 char:1
+ Move-ADDirectoryServerOperationMasterRole -Identity COMSRV2018 -Opera ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ResourceUnavailable: (COMSRV2018:ADDirectoryServer) [Move-ADDirector...ationMasterRole],
    ADServerDownException
    + FullyQualifiedErrorId : ActiveDirectoryServer:1355,Microsoft.ActiveDirectory.Management.Commands.MoveADDirectory
   ServerOperationMasterRole

Running thenetdomquery again it still indicates the fsmo roles being with the source server.

One obvoius effect is that I have a lot of red indicators in the target servers Daschboard which all say Online - restart pending

I am hesitant to just restart the server due to the error I got. Can someone advise what to do at this point?
My guide would tell me to:
Uninstall-ADDSDomainController -DemoteOperationMasterRole -RemoveApplicationPartition on the source server (but only after the Moving of the roles was successfull (which it wasn't in my scenario)

any suggestions on how to proceed?