When creating custom discovery data using the smsresgen class there is no way to remove this from the discovery related tables in ConfigMgr. Since there is a supported way to add this data, there should be a supported way to remove it. This is necessary as a rollback option, to return ConfigMgr to its default state, before the custom discovery data was added.

When System Discovery finds an object that seems invalid, currently it won`t be imported (which is good).
ERROR: System <systemname> is a unsupported operating system, unsupported version, or malformed AD entry. Reported system type is: ().
However if the same object has an AD Group Membership and AD Group Discovery finds it, it won't check if it is valid, but write the DDR and create the object record in SCCM DB.

Please change AD Group Discovery so it validates new objects too.

If I import a new computer using its MAC Address but later I install manually the client in the actual computer, two resources with the same name end up in the SCCM Database.
An option to make the default action merging both resources or just associating the client DDR to the manual import.