SQL Server 2017 was recently released on Oct. 2017. Microsoft team has made significant improvement in terms of performance on Models tree view control which is available under user and group permissions.
When user tries to change the permissions on tree view control at entity node it does throw an error like this "The Model Permission cannot be saved. The object guid is not valid".
This was identified after release SQL Server 2016 release, which is also present in 2017 RTM and will be fixed in 2017 CU1 accordingly.
Workaround was provided on MDS team blog. Please follow below link, further details are provided on it. Run the script described in this MDS (Master Data Service) team blog error applying permission on entity level
Here, MDS team has provided alter script of procedure [mdm].[udpSecurityPrivilegesSaveByMUID], which enables the end user to apply permissions on entity nodes as well.
