I’m trying to add an object reference to a layer using the Layer::AddMember method.

The method returns: ‘WARNING : 3051 - The object “MapMeshInstances.Instance2” cannot be added to the group’ . What’s funny, that at the same time the CStatus says “The operation completed successfully.”. 

The object I’m trying to add is a cloned polygon mesh, parented to a model object.

Is there a reason why it doesn’t work, especially that ‘MoveToLayer’, with the same arguments, works fine?

This sounds like a bug.
I also tried this method on XSI7.0, and I have the same warning message than you. But it’s not linked to the fact that the object is a clone, nor because it’s a child of a user model. It also happens on a simple null parented under the scene root model.

This sounds like a bug.

I came to the same conclusion. The ‘MoveToLayer’ command works fine, so at least there’s a walkaround to this problem.